This manual is one of the best resources for riders. It is reliable, classic, and sensible riding.
I especially recommend it for novice riders -- if you ride and handle your horse according to these guidelines, you will be safer, you'll have fun, and your horse will be happier.
The only caveat that I have is that the guidelines may not be totally consistent with specialized American sports like Quarter horse hunter classes which have their own fashions in some respects. Also, the terminology is British, not American.