One of the best book investments that we have made are the Sesame Street books A-Z. There is a board book for each letter and each book has a short story or rhyme focusing on that letter. If you turn the book over, they all connect to make a big floor puzzle with a picture of Big Bird with an item starting with each letter of the alphabet.
My kids have all loved them and I think that it really gave them a head start to their reading because they learned their letters so fast. Nathan can identify every letter in the alphabet. He loves to hear them at bedtime. Eric has started a new tradition of beatboxing while reading these books to Nathan. There is nothing like a little rap/beatbox to put a kid to bed! Now Nathan may have a beatboxing career ahead of him because I will catch him "a-pooh-pooh-choo"ing several times a day. It is SO funny to hear and he even has some sweet moves to go along with it.
What are your kid's favorite books?