Eh, I just read it in a library once when I was bored. I don't remember all of it, but I remember that I thought it was good. The book won a Pulitzer prize. The guy wrote a sequel to it but I haven't read it.I've got to read him. I've seen you recommend him some other place, too. I'll bet if you like him, he's damnably good.
Basically, in God: A Biography, Miles does a purely literary analysis on the Tanakh. He takes the set of stories as though it were a literary narrative, and examines the protagonist Yahweh and how he changes over time, and what his character and motivations are like.