The Hunters Guilde to Ballistics by Wayne Van Zwoll is an excellent book. I picked up a copy at a store that had it and started reading it. I was impressed, and bought it. It's one of the best gun books I've ever read. It's relevant to handloaders because it really explains, thoroughly but without being dull, concepts like headspace, and other important topics.
The book covers important historical developments, explains modern developments, and covers application of ballistics to hunting.