There are so many great children's books out there! We have a ton, but I work in a bookstore through out College so it's no surprise to anyone. The books my 5 month old loves the most right now are:
Guess How Much I Love You (she smiles when we help her do the actions in the book and we do them too)
Chicka Chicka Boom Boom
Brown Bear, Brown Bear
Mr. Brown Can Moo Can You
Jillian Jiggs
Fish, Swish! Splash, Dash!
and her cloth books that have crinkly stuff inside of them.