If you are looking for new books for your child to own I highly recommend Scholastic Book Clubs. Scholastic works hard to sell both new titles and popular books. You will find books on many subjects, and in a wide range of genres. Also, Scholastic has picture and chapter books.
When parents ask me what book will their third grader enjoy, I often recommend "Branches". It is a collection of books from scholastic. Branches are a set of books which are meant to help students move from shorter to longer chapters books. These book have great illustrations but they are right at the 3rd grade level (M-O). My past classes have especially loved the series, Dragon Masters and Hilde Cracks the Case , but, there are many others.
I buy almost all our classroom library books from Scholastic, and each time you place an order you help me do that as your order earns points. I then get to choose new books for our library, this is often how I get the newest books on the shelves. Thanks so much for helping grow our classroom library.