"A History of God" by Karen Armstrong
I am reading this book for the second time now, and let me tell you that it requires CONCENTRATION. If you're not careful, you'll get your Sumerians mixed up with your Akkadians, or your Muslim mystics mixed up with your Christian mystics, or your epistemology mixed up with your transcendentalism.
And then you'll be in a real fix, because you will look up from your book and realize that you have no idea what the last twenty pages were discussing. Then you will have to go read those twenty pages again, and that will be very frustrating, because this is a VERY long book.
Just the same, anyone interested in a comparative study of Christianity, Judaism, and Islam will probably like this book. It has a lot to say about what people have thought about God throughout human history, and if you can CONCENTRATE it will have you thinking. I liked it so much I read it a second time, and I don't often do that.
There are some who attack the author on the grounds that she isn't a "scholar." Apparently she studied history, but never quite completed her degree. I think that such an argument is founded upon jealousy, and on opinions taken second and third-hand from other sources. Like any historian, she is never right 100% of the time, and in putting her opinion out there she is taking a risk. Whether all her opinions are right or wrong takes little away from this book, since it is a masterful survey of a very, very big subject. A lot of "scholars" like to point fingers at Karen Armstrong, but until they start writing books this good I think they should keep their mouths shut, and their pens at rest.