I Love Trains! by Philemon Sturges and Shari Halpern: this is a very simple, very colorful book. It has a good rhythm and is easy to read aloud. This pair has collaborated on several other books including I Love Trucks and I Love Planes.... but I Love Trains is my personal favorite.
Trains by Byron Barton: even simpler than I Love Trains! and it's been issued both in paperback and as a board book. If you like this book... check out Barton's other wonderful books including Trucks, Boats, and My Car.
Trains by Anne Rockwell: more of a non-fiction book than the ones mentioned above, but it still works well for young kids. Probably more of a toddler book than a book for babies.
The Little Engine That Could by Wally Piper: you're reading right over this one, aren't you? Of course you know about this book, you don't need me to tell you about it. Well, maybe you don't know about a wonderful new version with illustrations by Loren Long. I think it's absolutely beautiful- and really enhances the story. Some people fall in love with it at first sight (like I did) and some people don't like it because it's not the one they grew up with. Give it a try... see what you think. And if you do like it... check out this wonderful page on Loren Long's website that features several sketches for the book along with the finished artwork.
Got any other good train book recommendations? (There are an enormous number of books published on this subject.) Let me know.... write them in the comments section of this post. I'm always looking for new easy books about trains (at least, my son is).