I'm A Big Brother
This one is the simplest of the 3 books we're reading. My 4 year old has it memorized, and my 2 year old loves it. It's perfect for his little attention span! It does a really good job of explaining the difference between what big boys can do and what babies can do (which is great since I know my 2 year old is going to have a really hard time giving up the "baby position").
The Berenstain Bears: New Baby
Baby on the Way
This is by far the most informative book we've read. Maybe a little too informative, although it's easy enough to "censor" for younger readers (maybe I'm crazy, but I don't think my 2 year old needs to be worried about how the uterus works quite yet). There is an illustration of a baby in mommy's belly, which my boys LOVE looking at; realizing that's what their baby sister looks like too.
So that's our current reading list in our home! What books did you read to your little ones to help prep them for a new baby?