The history of gospel harmonies, although little explored, particularly in the Middle Ages, is fascinating. For that reason, Brent A. Pitts's short volume is very welcome, as it fills an important gap in the historical development of the genre. A gospel harmony is an attempt to compile the four canonical Gospels of the New Testament (Mt, Mk, Lk, and Jn) into a single account that claims to remove the small discrepancies among the four evangelists' narratives and to stress the similarities between them in order to offer a smooth, linear, and full account of Jesus's life and deeds. The need for such a harmonized gospel was felt early in Christian history. Tatian in the second century provided the earliest and the most significant gospel harmony, known as the Diatessaron (ca. 172). Unfortunately, his text, probably written in Greek, although some of the best scholars hold it to have been composed in Syriac, has been lost and our knowledge of it mainly relies on excerpts and fragments quoted by early and medieval Christian writers, particularly Aphrahat and in the fourth-century Syriac commentary on the Diatessaron by Ephrem the Syrian. Arguably, Tatian's Diatessaron was very soon translated into Latin, possibly as early as 200 AD, since traces of it seem to be found in various vernacular gospel harmonies extant in medieval Dutch, German, and Italian. In any case, a Latin gospel harmony is found in the codex Fuldensis, the oldest of all harmony witnesses preserved in the West, compiled in Italy before the middle of the sixth century, proofread by Victor of Capua between 541-546, and later owned by St. Boniface, which is why it is now housed in the Stadt- und Landesbibliothek of Fulda under the signature "Bonifatiushandschrift," no. 1. If we can trust Victor of Capua's preface to this gospel harmony, there is no good reason to doubt the harmony to be Tatian's.
The Anglo-Norman gospel harmony, preserved in a single copy within a Dublin manuscript (Christ Church Cathedral C6.1.1, Liber niger), is the latest to have been discovered. Pitts, who also provided the first critical edition of the text,  convincingly dates it between about 1170 and 1294, more precisely although tentatively, in the middle of the thirteenth century. He also suggests that Thomas of Hales (fl. ca. 1250) might be a potential author. Be that as it may, the Estoire de l'Evangile is a good example of a vernacular gospel harmony that appeared after a long period of rather intense production of Latin gospel harmonies in the twelfth century--by Odo of Cambrai, Rupert of Deutz, Wazelin II, Zachary of Besançon, Clement of Llanthony, Peter Comestor, and Peter Cantor--, in a time of great revival of teaching and learning the Gospels in the West. The Anglo-Norman gospel harmony is also of a particular interest, since it is very likely the long-sought source of the later famous Pepysian gospel harmony (ca. 1400) edited in London in 1922 by Margery Goates (Early English Text Society. Original Series, 157).  As Pitts shows it (14-18), the similarities between the two harmonies are striking. One of them is the arrangement of the miracles and teachings of Christ in seven major sections called "meditations," which makes of these two harmonies an exhortation to a daily meditation on Jesus's life.
In the same line, Pitts holds that Clement of Llanthony, prior of the Augustinian monastery of Gloucester who flourished in the mid-12th century and author of a Concordia quattuor evangelistarum, cannot be a source of the Anglo-Norman gospel harmony, even though he is named in the prologue of it. Pitts gives several arguments in support of his views (12-14). In footnote 5 of his introduction, he refers to a critical edition of Clement's gospel harmony, which Cherish Ahlgren was working on some ten years ago at the University of Birmingham. Unfortunately, this critical edition does not seem to have been completed yet. However, part of the middle English translation of Clement's gospel harmony has been the subject matter of a doctoral dissertation defended by Paul M. Smith at the University of Nottingham in 1984 and now available in print in two volumes. 
To conclude: Pitts's book has been made with great care and is well conceived and organized. It is composed of a solid introduction, complemented by a concise bibliography and followed by the expected annotated English translation of the Gospel. As far as I can see, Pitts's modern English translation of the Anglo-Norman gospel is reliable and accurate, and the footnotes aim to call attention to textual and philological peculiarities of the work. Three appendices consisting of a table of biblical sources of chapters of the gospel, a synopsis of five passages from the Estoire and the Pepysian Gospel Harmony (Gifts from the East; Jesus walks on the water; Jesus raises Lazarus; Magdalene at the tomb; and Pentecost), as well as a list of proper names, nicely complement Pitts's volume, which will be of interest for all researchers in biblical and religious studies, as well as for people interested in medieval English and French studies.
1. Brent Pitts (ed.), Estoire de l'Evangile (Medium Ævum Monographs 28; Oxford: Society for the Study of Medieval Languages and Literature, 2011).
2. See also William L. Petersen, Tatian's Diatessaron: Its Creation, Dissemination, Significance, and History in Scholarship (Supplements to Vigiliae Christianae 25; Leiden: Brill, 1997), 168-170.
3. Paul M. Smith, "Oon of Foure: The Wycliffite Translation of Clement of Llanthony's Latin Gospel Harmony Unum ex quattuor (parts I-V) (London: theuniversitiespress.com, 2015, ISBN: 9781320954068). The same author recently published another study on the topic: "Clement of Llanthony's Gospel Harmony Unum ex quattuor and Augustine's De consensu evangelistarum," Church History and Religious Culture 94.2 (2014): 175-196.