This is seminal book of Girard's. In his investigation of myth he uncovers what he calls the scapegoat-mechanism, the tendency of society to collectively transfer guilt onto a sacrificial victim.
An introductory chapter on fourteenth century European anti-semitism leads into a discussion of various myths from around the world, all "texts of persecution." Girard's thesis, that basically all founding myths feature the sacrifice of an innocent victim, proceeds in good structuralist fashion: these tendencies are an innate part of human nature.
But he doesn't stop there. Taking a somewhat eschatological stance, midway through the book he continues to tackle what he calls the ultimate uncovering of the scapegoat mechanism: the death of Christ. His argument is, roughly, that Christ in his words and deeds, and finally in his self-sacrifice, demonstrates how he understands this inborn but not irredeemable human characteristic. The rest of human history thus unfolds towards a greater understanding (and Girard's work is part of this) of the irrationality of sacrifice--slowly we start to fulfill the promise of our humanity, and work towards a society in which no sacrifice will have to be made.
The most gripping chapter for me is that on Peter's betrayal. This is a truly remarkable reading of the wellknown biblical narrative, a reading that simultaneously redeems Peter (somewhat) and condemns all of humanity. Jesus, the ultimate innocent victim, understood this, as does Girard: if Peter fails, we all fail.
Since I am not a student of myth I feel I can't comment on Girard's reading of myths, most of which I hadn't heard of before, but it certainly sounds convincing. Especially his reading of the bible makes this book worthwhile to students of language, literature, social sciences, and morality.