See Common Prayers: Faith, Family, and a Christian’s Journey Through the Jewish Year (Boston: Houghton Mifflin, 2001), pp. 139–146, by Protestant theologian Harvey Cox, for some thoughtful comments on this subject. Another relevant book is John G. Gager’s Reinventing Paul (New York: Oxford, 2000), which argues that Paul’s supposed supersessionism has been interpreted out of context and that Paul’s message was meant for Gentile Christians. Paul, who never gave up being Jewish himself, expected Jewish Christians to continue to be Jews as part of their faith in Jesus.