This is the book I refer back to time and time again for everything eventing related particularly fitness. It was written in 1990 but is still relevant today.
Ginny was ahead of her time for many things and though some of the equipment is outdated the horsemanship, stable management and the lengths that they went to in order to produce top horses shines through.
The book takes you from an unbroken eventer right up to 4* and includes advice on how to break your horse, introduce the work and what they should be doing along the line. The fitness grid is still the best I have seen giving you advice on how for the horse needs to be for novice event (I read this as BE100/Novice now as things have changed quite a bit) and right up to preparing for your first three day.
Everything is well explained and I often read the book time and time again and pick up something new which is appropriate to where the horse is in his competitive career.
The joy of this book is that you can find it cheap on Ebay and on Amazon because of its age.