Get him some great board books -- he will enjoy them for at least three more years. Some recommendations:
The Maisy books by Lucy Cousins
The Max and Ruby books by Rosemary Wells
Owl Babies, Martin Waddell
The Very Hungry Caterpillar, Eric Carle
The Very Busy Spider, Eric Carle
The Very Lonely Firefly, Eric Carle
The Pigeon Loves Things That Go!, Mo Willems
Hug, Jez Alborough
Brown Bear, Brown Bear, What Do You See?, Bill Martin, Jr.
I Went Walking, Sue Williams
Goodnight, Gorilla, Peggy Rathmann
I'm a preschool teacher, and used to teach kindergarten. I can't emphasize enough how important it is to instill a love of books in your children. Teachers can always tell who gets read to daily at home -- and who doesn't.
If you aren't already making books a part of your daily routine, stock up on some great books and enjoy, enjoy, enjoy!