I have been waiting my whole career for this book. In 1986 I arrived in Cambridge, England, as a postgraduate hoping to work on the medieval devotion to the Virgin Mary, ideally in its most "popular" form. I had of course been reading R. W. Southern's eloquent account of the transition "from epic to romance" in high medieval attitudes toward life, love, suffering, sin, and the divine (The Making of the Middle Ages [New Haven: Yale University Press, 1953]), and I was particularly intrigued by what I learned there about the collections of Miracles of the Virgin that, Southern argued, had begun to appear in England in the early twelfth century. According to Southern, these collections not only "came in time to occupy a position at the very centre of medieval personal devotion" (Making of the Middle Ages, 248). They were also "among England's chief contributions to the popular literature of the Middle Ages" ("The English Origins of the 'Miracles of the Virgin,'" Mediaeval and Renaissance Studies 4 : 176-216, at 205). Surely if I wanted to understand either the devotion to the Virgin Mary or its role in the development of medieval English and Continental popular literature, I needed to learn more about these collections, particularly those which Southern had identified as compiled in England between about 1120 and 1140 by the monks Dominic of Evesham and William of Malmesbury. There was only one problem (or so it seemed to me as a beginning graduate student): two students at Oxford had already edited both collections, J. C. Jennings (B. Litt., 1958) and Peter N. Carter (D. Phil., 1959).  What more needed to be done? Nothing (or so it seemed to me as a beginning graduate student). But actually, of course, everything.
While clearly confirming the significance of the collections that Southern had highlighted, neither Carter's (William) nor Jennings's (Dominic) edition was ever published. In 1968, the Claretian José-María Canal published his own edition of William's collection (Rome: Alma Roma Libreria Editrice), and in 1998, he brought out an edition of Dominic's (Studium Legionense 39: 247-83). Like Carter's and Jennings's unpublished editions, however, Canal's have remained relatively inaccessible, the more so for Anglophone students as their introductions are written in Spanish. The scholarly situation for the past sixty-odd years has, accordingly, been more than a little ironic. On the one hand, Southern had insisted that the English collections of Miracles of the Virgin belonged at the center of the study of the "new ways of thinking and feeling about the world" that emerged from the monasteries in the twelfth century (Making of the Middle Ages, 246); on the other, despite Southern's testimonial, almost nobody other than Jennings, Carter, and Canal was drawn to study these collections in any depth, whether for what they might tell us about the devotion to the Virgin or as a literary form.
So, for example, A. G. Rigg included only a brief entry (about half a page) on "Miracles of the Virgin" in his magisterial History of Anglo-Latin Literature, 1066-1422 (Cambridge: Cambridge University Press, 1992), noting simply of William's: "The miracles are in a direct but elegant prose, and were intended for the encouragement of the simple" (p. 35). Likewise, in studies of the larger tradition of Marian miracle stories, the early twelfth-century Anglo-Latin collections have been typically mentioned only in passing as the background for the much more studied vernacular collections made on the Continent by poets like Gautier de Coinci, Gonzalo de Berceo, and King Alfonso X of Castile, with one significant exception: what they can tell us about Mary's relationship to the Jews.  Literary scholars are familiar with this trope above all thanks to Chaucer's "Prioress's Tale," as well as from its prominence in the story of Theophilus, the first of the stories included by William and the second in Dominic's collection. Nevertheless, as Robert Worth Frank, Jr., pointed out some time ago, stories about the Jews, while a regular component of the genre, constitute only a small percentage of the stories as a whole.  William's collection of fifty-three stories contains only six involving Jewish characters, only three of which actually involve a miracle of the Virgin (1. Theophilus, 32. Jew lends to Christian, 33. Jewish boy), while a fourth involves miracles associated with her images (51. The Virgin's image insulted).  Dominic's collection of thirteen stories contains only two involving Jewish characters, albeit both are properly miracles of the Virgin (1. Jewish boy, 2. Theophilus). Fully to understand the significance of these stories for the devotion to the Virgin as well as the history of English and Continental literature, we need to be able study all of the stories in the context(s) in which they originally appeared.  Thanks to Thomson and Winterbottom's exemplary edition and facing-page translation, with William's collection we now can. (They detail their respective contributions in their Preface; in what follows, I am taking them as a team.)
William's collection survives as a collection in only two manuscripts: Salisbury, Cathedral Library MS 97 (s. XIII in.), fols. 91-114v (Prologue, 53 stories, Epilogue) and Paris, Bibliothèque nationale MS lat. 2769 (s. XIII in.), fols. 55-84v (Prologue, 29 stories). The Salisbury manuscript was first described in 1891 by Adolf Mussafia in the course of his groundbreaking survey of the larger tradition of Marian legends, while the Paris manuscript was only (re)discovered some sixty years later by Henri Barré.  As Mussafia realized for the Salisbury manuscript (S) and Carter confirmed in his comparison of S with the Paris manuscript (P), neither manuscript represents the full collection in the final form in which William intended it to be read. Although S contains all (or presumably all) of the stories, their ordering does not follow the scheme announced by William in the preface to Julian the Apostate, the second story in P but the twenty-fifth in S. According to Carter as confirmed by Thomson and Winterbottom, "S reflects a primitive state of the ordering of the miracle stories, P a state revised by William himself" (xxxi), but as P is incomplete, some place for the stories included in S needs to be found. In their edition, Thomson and Winterbottom follow Carter's ordering of the stories, coming to the same conclusions, as they say, "by a different route" (xxx). And yet, they confess that even thus confirmed by their analysis, this ordering represents only "the best we can do," summarized in table form on pp. xli-xliii. Unlike Canal, who followed Carter's ordering for the most part without explaining why, Thomson and Winterbottom have taken pains throughout their edition to show their work, providing both a concordance for all four orderings (lx-lxii: S, P, their edition, Canal), as well as giving not just the manuscript sigla but also folio numbers for every story as it appears in the manuscripts. The reader is, therefore, enabled to reconstruct at every juncture the juxtaposition of the stories both as (conjecturally, at least) William intended to order them and as his copyists reordered them.
As Thomson and Winterbottom make clear, both S (fol. 91v) and P (fol. 55r) begin with a Prologue in which William explains his general purpose in praising the Virgin according to the four classical virtues found in her (Justice, Prudence, Courage, and Temperance). Likewise, both S and P begin with the story of Theophilus as told in "a quite old source" (15) (S: fol. 93v; P: fol. 60v). Thereafter, however, they diverge, S (fol. 95r) continuing with Guy of Lascar in which Mary is "manifested to be the Lady of all nations in every part of the world" (45), while P (fol. 63r) moves to Julian the Apostate in accordance with William's plan "to show that the blessed Virgin has poured out the bowels of her compassion on every rank, every condition of men, and on both sexes" (omni hominum gradui, omni conditioni, utrique sexui), starting with "bishops, the highest type (summum genus) of men" (21). Using P as their touchstone in their reordering of the stories, Thomson and Winterbottom have attempted to group them, in William's terms, "by time, place and type" (res temporibus diuersae, locis discretae, generibus promiscuae) (21), taking genera to mean the "rank" of the characters involved in the stories (xxxii). Accordingly, by this ordering, in Book I we find stories about bishops (nos. 1-12), abbots (nos. 13-14), sacristans (nos. 15-16), and monks (nos. 17-24), while in Book II we find stories about clerks (nos. 25-28), priests (nos. 29-30), laymen (nos. 31-39, including two stories involving both Mary and Jews), women (nos. 40-44), trivia (nos. 45-48), and images of the Virgin (nos. 49-53, including one story in which a Jew insults Mary's icon at Blachernai by throwing it into a latrine: "The sacred image, brought up from the filth, poured forth a long stream of oil, what a wonder!" ).
Other groupings are, however, suggested by the ordering of the stories as they appear in S, for example, by region (see table at p. xxi for the different locations of the miracles), as well as by the choices made by other compilers taking individual stories or sets of stories from William's collection as a whole. Carter identified fourteen additional manuscripts in which selections from William's collection appear, to which Thomson and Winterbottom have added one (Oxford, All Souls College, MS 22, s. XVI med.). All but three of these manuscripts (all briefly described, including their provenances, on pp. xxvii-xxix) come from England. The latter three, discovered by Carter, are French. Thomson and Winterbottom used seven of these additional manuscripts in preparing their edition of the stories (sigla included in the table on pp. xli-xliii). According to Thomson and Winterbottom's analysis, most of these subsidiary manuscripts "support P against S in roughly 75% of the instances registered in the apparatus" (lv), suggesting once again that P represents the stories in their more polished form. Nevertheless, they caution: "But often we cannot be sure. Interested readers are therefore asked to keep their eye on the apparatus, and judge for themselves if we have been right to reject (or in some cases approve) the P reading" (lv).
To complicate the tradition of William's collection only further, Canal identified a further five manuscripts containing only William's Prologue but no stories; two of these manuscripts come from England, the other three from the Continent. Thomson and Winterbottom consulted two of these manuscripts (one from Exeter Cathedral [MS 3505, s. XIV med.], the other from St. Sernin, Toulouse [Lyon, Bibliothèque municipale, MS 622, s. XIV]) for their edition of the Prologue so as to illustrate the form in which the Prologue circulated as a free-standing treatise. They leave open the question, however, whether there are more manuscripts to be found either of the Prologue or the stories as told by William, noting that Carter looked "at most of those in Paris. But no one has done for France (or Germany) what was done for Italy with exemplary patience by M. V. Gripkey" (liv, n. 124).  For those wanting to venture further into the intricacies of the manuscript tradition, Thomson and Winterbottom include as an appendix a Handlist of manuscripts now in Great Britain, Ireland, France, the Low Countries, Germany, Austria, Switzerland, Scandinavia, Italy, Spain, Portugal, and the United States containing Miracles of the Virgin in Latin, with the caveat lector that "a good many of the collections in them are as yet unidentified" (137, n. 1).
If, in Thomson and Winterbottom's words, "it looks unlikely from [Gripkey's] findings that the influence of William's book spread so far [as Italy]" (liv, n. 124), we nevertheless cannot be sure. If there is one thing that their edition and (it should be said, elegant) translation shows, it is how much work there still is to be done before we appreciate fully the significance not only of William's collection of Marian miracles, but of the tradition to which he contributed so signally as a whole. At least now, however, we have a reliable, meticulously referenced, readable, and easily accessible place to start. 
1. A third collection, found in Chicago, Regenstein Library Special Collections MS 147 and identified by Southern as a version of that compiled by Anselm of Bury St. Edmonds, was edited by Elise Forsythe Dexter, Miracula Sanctae Virginis Mariae, University of Wisconsin Studies in the Social Sciences and History 12 (Madison, 1927).
2. On this aspect of the tradition, including the stories in William's and Dominic's collections, see Adrienne Williams Boyarin, Miracles of the Virgin in Medieval England: Law and Jewishness in Marian Legends (Woodbridge: D.S. Brewer, 2010).
3. Frank calculated that Jewish characters appear in "7 1/2 percent of the common stock of miracles" from the whole medieval period. See his "Miracles of the Virgin, Medieval Anti-Semitism, and the 'Prioress's Tale,'" in The Wisdom of Poetry: Essays in Early English Literature in Honor of Morton W. Bloomfield, ed. Larry D. Benson and Siegfried Wenzel (Kalamazoo: Medieval Institute Publications, 1982), pp. 177-88, at p. 179.
4. The other two stories in William's collection with Jewish characters are not properly miracles of the Virgin. Although the one (4. Toledo) takes place on the feast of the Assumption, it is in fact a story about an attack on the Jewish community in Toledo inspired (as William tells it) by a woman's voice lamenting that her Son was being insulted. The other (5. Jews of Toulouse) has even less to do with Mary. The tensions between Jews and Christians are real, but the specifically Marian element is missing. William justifies including this story in his collection because in it "an injury to her Son was appropriately requited in a way that brought glory to the blessed Mary" (27). On this latter story, see Kati Ihnat, "Getting the Punchline: Deciphering Anti-Jewish Humour in Anglo-Norman England," Journal of Medieval History 38.4 (2012): 408-23.
5. For an important study of their liturgical context, see Kati Ihnat, "Marian Miracles and Marian Liturgies in the Benedictine Tradition of Post-Conquest England," in Contextualizing Miracles in the Christian West: New Historical Approaches, ed. Matthew M. Mesley and Louise E. Wilson, Medium Aevum Monographs n.s. 32 (Oxford: The Society for the Study of Medieval Languages and Literatures, 2014), pp. 63-97.
6. Adolf Mussafia, "Studien zu den mittelalterlichen Marienlegenden," Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften zu Wien (Phil.-Hist. Klasse) 123 (1891) Abh. viii, 1-85, at pp. 18-30; Henri Barré, "Le 'De quattour uirtutibus Mariae' et son auteur," Ephemerides Mariologicae 3 (1953): 231-44.
7. Mary Vincentine Gripkey, "Mary Legends in Italian Manuscripts in the Major Libraries of Italy," Mediaeval Studies 14 (1952): 9-47, and 15 (1953): 14-46.
8. With one quibble: there is no bibliography of the extensive scholarship referenced in the notes to the Introduction or the individual stories, nor do the scholars appear in the General Index.