For Christmas we got him Trains Go by Steve Light. It is adorable and just has different sounds trains make. His favorite is the mountain train that goes "Trip Trap Fuff Puff." Every time he sees the picture he starts going, "Fuf! Fuf! Fuf!" The illustrations are my favorite part, though. Each picture is such a work of art.
There is also a Trucks Go version that looks just as cute!
What are your kids' favorite books? I'm always looking for great new ones!