Purchased 2 books, but only received one

you can simply make a claim with amazon stating what happened. Theyll get your money back for you and you might be able to keep what they did end up sending.
view your recent orders under your amazon account. they have a selection called "problem with an order" make sure to have that order information handy.
its really easy, and amazon supports its buyers.

Call up amazon customer services and explain. They are generally very helpful and aim to fix your problem the moment you report it. The details can be ffound by going to your account on amazon