The Falconer's Apprentice: William C. Oakes. THIS IS THE BOOK that every apprentice should read. It's very cheap and very clearly written.

The Red Tailed Hawk: Liam McGranaghan (hard to find but I just learned you can rent it from Davidson's falconry website.

American Kestrels in Modern Falconry: Matt Mullenix. This is a great read even if you don't plan on taking a Kessie. They're really fun birds to read about.

The CHC study guide and manual are absolutely the best. Probably 80% of the questions on the IL test are from that book.

North American Falconry and Hunting Hawks is AWESOME if you can borrow it from somewhere (check the library), it's very expensive to purchase.

Buteos and Bushytails is a good one if you plan to hunt squirrels with a RT. Again, out of print, so see if you can track down a copy to borrow.