This book explores both the emergence of monotheism in ancient Israel and offers a critique of other theories which have been proposed about that topic. Gnuse offers a very exhaustive listing of the scholarship in the area, outlining all the major theories, and potential drawbacks. Some areas of contention he discusses are whether or not the coming of monotheism was early (Iron Age) or post exilic , whether Asherah was viewed as Yahweh's wife, whether the coming of monotheism was a revolution or the result of a major sudden breakthrough and whether or not the Israelites kept themselves distinct from their Canaanite neighbors or were, effectually, Canaanites themselves. Gnuse argues that monotheism emerged out of a natural mixing of highland and lowland Canaanites interacting with foreigners and their gods and concretized in the post-exilic era, complete with a devil about 200 BC.
All of this was interesting. Where he lost me is his insistence on using biological evolution as some kind of paradigm by which to compare the 'evolution' of the ideas of monotheism. I don't think he gains anything at all by this comparison and his ideas of biological evolution seem a bit confused. He clearly thinks that monotheism is overall superior, more sophisticated, encouraging more ethical thought etc., whereas biological evolution has no such valuation or teleology. Parts of his monograph became excessively repetitive and particularly boring were some of his criticisms of the larger paradigms scholars often use to understand what happened in Israel, such as Eliade's.
Overall it was useful and I learned a lot, but the length of the book could have easily been lessened by a third.