I bought a couple and then borrowed some from friends and my library also. By far the best was Up The Duff by Kaz Cooke. I found it had all the info needed, presented in a humorous and non-scary way. It also has a week by week guide (with a VERY funny diary) with a ruler each week showing how long you baby is.

Another good one is "What to expect when you're expecting" but this was a bit bland.