The Suffraganeus bibliothecae, most likely composed some time in the 1140s by the Roman scholar Nicolaus Maniacoria before he left the Lateran to become a Cistercian monk, is an unusual Bible commentary (surviving, incomplete, only from Genesis through to the Psalter) devoted to the textual criticism of the Vulgate text of the Old Testament. It is here edited for the first time: it had hitherto attracted attention only for its prefatory material and the commentary on the Hebrew Psalter. Other works by this little-known author include an edition of the Psalterium Romanum (of which only the preface has been published), the Libellus de corruptione et correptione Psalmorum et aliarum quarundam scripturarum (devoted to the textual criticism of the Gallican Psalter, edited by V. Peri in 1977), and the still unpublished vitae of his mother Constantia, who commissioned some of his writings, and St Jerome, who was in many ways his role-model. Maniacoria, as Cornelia Linde's wide-ranging German-language introduction reveals, demands our attention not just for his contributions to the principles of biblical textual criticism (with interesting differences between theory and practice), but also for his engagement with the Hebrew text of the Old Testament. He can be placed, broadly speaking, in the orbit of what Smalley called the ‘school of St Victor’ (he quotes Hugh extensively, and yet was probably writing somewhat earlier than Andrew, who was some ten years his junior), but Linde associates his access to the Hebrew Bible and exegesis more with the Jewish community in Rome, where he plausibly claims to have had personal contact with Jewish scholars. Indeed Linde, although a master of scepticism, thereby presenting us with a quite new view of Maniacoria's life and works that is much better founded than hitherto, is willing to go as far as to suggest direct contact with the Jewish scholar Abraham ibn Esras, who, like the author of the Suffraganeus, was living in Rome in the 1140s. The critical edition, which is based on the two extant manuscripts, is expertly presented and stands out for its wonderful apparatus documenting the relationship to Vulgate readings, sources and parallels. It provides an excellent foundation for further study of the Bible in the twelfth century, the history of biblical textual criticism, and the interaction of Jews and Christians in medieval Europe.