I signed up through Plum District (deal no longer available) to try the Little Book Club. I got one for my 14 month old and one for my almost 4 year old. The books are normally 25.00 a month but I got them for 13.00 this month. Each month you get 3 books (at least 2 hardcover) to go along with a theme. If you already have a book they send, they will credit your account 12.50. They ship Media Mail, so it can take a bit to reach you, but they are worth it.
My Almost 4 Year Old’s Books