It's a wonder that this book was not written many decades early, for it takes up a hugely important and fascinating topic. Its premise is that Judaism and Islam (but not Christianity) are traditionally both "religions of law" in the sense that they share a premise that "God governs in the here and now through revealed law"; and both make living by that law central to everyday life. Some of the details of those laws are very close in spirit and detail (the prohibition of pork, male circumcision) while others are different or even opposite in detail (mentioning the name of God).
Looking at the whole, how similar or different are the two laws and faiths in their classical forms of a millennium ago?1 The authors offer a nuanced reply: "when we see Islam and Judaism from a distance and in the perspective of other world religions, they concur on much, but when we set them side by side in close proximity, … they find difficult the identification of common thought and expression." The present volume looks at these questions in outline; the authors promise a second book that will take up the details. The outlines include a comparison of the founding documents of the two religions, the intellectual sources of the law, legal institutions, legal personnel, plus a most interesting look at the "disproportions," meaning those aspects where the two do not parallel each other (Sabbath vs. hajj, Jerusalem vs. jihad).
Neusner (a specialist on all things Jewish and one of the most prolific authors in America today) and Sonn (a scholar of Islam) provide an exemplary balance and reach sensible conclusions. They show, for example, how historical circumstances fostered characteristic differences: "Islam could theorize but also had to govern. The sages of Judaism had the luxury of thinking about matters far beyond their control." Despite the many differences between the two faiths, the authors reach this striking conclusion: "If we explained to one side the details of a case facing the judges of the other, chances are the jurisprudents of both religions would reach a decision in accord with the same rules of reasoning – and would reach the same decision."
1 A millennium ago, not today: the impact of modern ways has changed both religions, but Judaism much more, in that something like two thirds of Jews today do not live strictly by the law.