For the hunters:
The first book that I would recommend for a hunter rider is George Morris's Hunter Seat Equitation. It is a classic and it contains lots of photos and explanations of how to ride over fences correctly, as well as exercises that can be used to make your riding better.
Even if you do not plan on competing in any equitation classes, this book will explain how you should be riding in order to show your horse well in hunter classes.
You Be The Judge: Introduction by Ian D. Millar; Foreword by George H. Morris
The next book that I would like to recommend is Randy Roy's You Be The Judge. You can also look for earlier versions, called Here Comes The Judge or The Judge Is Back.
This book is concerned primarily with showing. The author, who judges the hunter and equitation rings, goes through the different classes and explains what he's looking for as well as what he doesn't want to see. You will learn the difference between the major faults and the minor faults and then get a chance to judge "classes" of photos to evaluate your own judging ability. This is a great way to start seeing the world through a judge's eyes.
For the jumpers:
My favourite jumper book at the moment is Training the Modern Jumper by Elmar Pollman-Schweckhorst. It is an honest training guide and it covers everything from choosing the right horse to dressage for jumpers to what modern course design demands from our horses.
This is a very well-rounded look at training, with sections on ethics, hoof care and common lameness problems that affect jumpers included.