R. Crumb created Mr. Natural, Fritz the Cat and "Keep On Truckin". He wanted to do an illustrated satire on the story of Adam and Eve but a friend talked him into doing the whole book of Genesis.
Crumb said he found Genesis just too bizarre for satire, so he decided to do it straight.
The new book is excerpted in The New Yorker (sub) and you can see Crumb's famous style at work in this lo-res scan. Via Boing Boing.