This book describes how the Jewish (and subsequently Christian) religions emerged from a rather different set of beliefs and practices. The ancient Israelites and Judahites did not practice what came to be the Jewish religion. They worshipped a god called Yahweh, but they did not believe he was the only supernatural being. Sometimes they were monolatrists – that is, they only worshipped this god, even though they believed there were others. Sometimes they made side bets and also paid homage to other gods, including Baal (like Adonai, a title rather than a personal name), Anat and Asherah. It's easy to see the evidence of this in the Bible itself, once you read it with an open mind rather than from a perspective that believes the patriarchs, and the Israelites, were proto-Jews. West's book is nicely footnoted with proper references to the Biblical text without being dry and academic. He has a good feel for some of the linguistic issues in the text too – pointing out examples when it uses unfamiliar words for what would have been familiar objects, and thinking through what the significance of that might be.
He has a nice little riff on Polytheism vs Monotheism at the end, which I personally find quite compelling because I've been thinking on the same lines myself. We hear so often that Monotheism is morally and intellectually superior to Polytheism that we rarely stop to think why that might – or might not – be true. I'm not any kind of theist, but once you start to think about it Polytheism seems to make more sense of the world and its moral challenges than Monotheism.
It's only a little book, but it is a great gateway to the world of Biblical studies; proper Biblical studies, that is, not the kind of brain-numbing indoctrination that religious organisations' bible classes peddle. Once you acknowledge that the Bible is a collection of different books, written at different times by different people with different sorts of objectives, you can really begin to appreciate and enjoy it. It's both familiar (in that we know a lot of the stories and the characters) and strange (in that there is a huge amount of material that we just ignore because it doesn't fit into our religious schema). As an atheist I go back to it often, and never fail to find something both new and enjoyable. I'll keep West's book next to me when I do, and I'd be delighted to find more books by him.
One tiny little quibble; this is a popular introduction to academically respectable theological and biblical studies. So why no reference to another such book, “Who wrote the Bible?” by Richard Elliot Friedman, which is also a great account of the documentary hypothesis? Perhaps there's a good reason, but it seemed a surprising omission to me.