The French Protestant Isaac Casaubon (1559–1614) is renowned as a great classical scholar and philologist, with particular expertise in Greek. What has generally been overlooked, however, is the extent to which Casaubon also engaged with Jewish materials. Yet, as Anthony Grafton and Joanna Weinberg demonstrate in this highly engaging study, a concern with Hebrew scholarship permeated his entire career. Indeed, this concern is evident wherever one looks: in Casaubon's substantial extant correspondence, the hundreds of books which formed his library (many of which are heavily annotated), as well as his diary, notebooks and published writings. It is only by reading these in conjunction with one another, they contend, that one can truly understand how Casaubon thought and worked – a frequently repeated image is of him reading ‘pen in hand’ – and in turn how his Jewish interests intersected with his better-known activities. In fact, as the authors acknowledge in the opening chapter, the sheer extent of the surviving materials make an exhaustive account unfeasible; instead, the volume is framed around a number of suggestive case studies. In the second chapter Grafton and Weinberg seek to uncover how Casaubon read his Hebrew texts. These included grammatical, kabbalistic, philological and exegetical works. His approach to the Bible is particularly instructive: he treated it as he did ancient classical texts, reading it in light of the best commentaries (including Jewish ones), committing extracts to memory, and valuing its literary as much as its spiritual qualities. In the third chapter the authors consider Casaubon's broader engagement with Hebrew studies. At the heart of this chapter is a consideration of the critical manner in which Casaubon read Johann Buxtorf's guide to contemporary Jewish life. In the fourth chapter attention turns to Casaubon's published writings, and particularly his Exercitationes, an 800-page attack on the Annales ecclesiastici of Cardinal Cesare Baronio. Casaubon's prime intention was to highlight Baronio's ignorance of Hebrew; this in turn fed into his efforts, as a Calvinist, to undermine Catholic claims to be the rightful heirs of the early Christian Church. In the final chapter Grafton and Weinberg turn to Casaubon's interactions with two of his Jewish contemporaries: Julius Conradus Otto, a convert from Judaism and professor of Hebrew, and Jacob Barnet, a learned Jew who promised to convert; both relationships further reveal Casaubon's enthusiasm for Hebrew learning, but also the tensions which this could provoke. The volume concludes with three appendices: the first of these, written by Alastair Hamilton, is concerned with Casaubon's engagement with Arabic; the second contains a discussion of Casaubon's views on the Masorah; and the third lists more than forty Jewish books that he is known to have owned. In demonstrating the extent to which he engaged with Hebrew materials, Grafton and Weinberg have added hugely to our appreciation of Casaubon, but through their own meticulous scholarship they have also greatly enhanced our understanding of early modern scholarly practice, and indeed the extent to which Christian Hebraism could be part of this.