Note that classy Oxford comma in the title.
See what Daniel Boyarin, John Barclay, and Daniel Schwartz say about it:
"Contesting Conversion addresses an important topic in a fascinating way. It's convincing, makes a highly significant argument cogently, and is extremely well written. The remarkable thing about the book is that Thiessen demonstrates, over and over, that texts that have been understood to support the idea of conversion via circumcision say precisely the opposite. It is not that he has come with an agenda to the texts and discovered that for which he searched, but rather that scholarship till now has done that. Thiessen removes the scales from our eyes."---Daniel Boyarin, Professor of Near Eastern Studies and Rhetoric, University of California-Berkeley
"This is a fine piece of historical investigation which successfully challenges a scholarly consensus. Exploring the insistence on eight-day circumcision in the Hebrew Bible, some strands of Second Temple Judaism, and Luke-Acts, Thiessen unearths a robustly genealogical conception of Jewish identity that defies modern notions of religion. The result is a highly significant contribution to current debates about conversion, Jewishness and ethnicity in ancient Judaism and early Christianity."---John M. G. Barclay, Lightfoot Professor of Divinity, Durham University
"Contesting Conversion argues convincingly, on the basis of a wide range of biblical and post-biblical evidence, that the notion that being a Jew is determined by birth alone, and so cannot be affected by choice, was current in antiquity and alive and well among many Jews in the Second Temple period down to the first century C.E. With regard to circumcision, which many took to be part of a process of conversion, Thiessen argues that many other Jews limited its religious efficacy to male Jewish babies and therefore denied that it could turn a Gentile into a Jew. This book is a welcome and important balance to research into the ethnic vs. religious nature of ancient Jewishness, especially insofar as such research often builds its notions on the basis of rabbinic and Christian universalism."---Daniel R. Schwartz, Professor of Jewish History, Hebrew University