Mr g: A Novel About the Creation by Alan Lightman.
Mr g (God) lives in a void with his Aunt Penelope and Uncle Deva. He awakes from a nap one day and decides to create a universe, and then several universes. In the process he also unwittingly creates a Satan-like entity.
I'm a short way into the book, Quantum Physics has been mentioned and to be honest it's all a bit beyond me at the moment. Thankfully it's quite a short book so I may get to the end before I give up.
Alan Lightman is apparently a distinguished physicist and author of Einstein's Dreams. According to the blurb, the book takes us from the Big Bang to the end of the Universe.