Centered Riding
by Sally Swift
This is a great guide to any style of riding. Innovative teaching methods that work is what it boils down to. The methods are easy for young children to understand because there are a lot of imaginative descriptions and illustrations, but at the same time, will not dumb down riding for adults. It's not a how-to book, but more of a new way to look at your riding from the horse up. It's been around for years, and it's still on every horsepersons' shelf, and for good reason.
This is a great book that takes the basics and gives you some alternative ways to think about them.