Take a look at the book "Overcoming Gravity" by Steven Low, which is by far the best Gymnastics book known to me. I suggest reading the Amazon reviews for more details.
What I personally like about this book:
Many books on strength training tell you how to train, but not why to train this way. This book goes into detail with all the relevant topics -- what kinds of motor units/muscle fibers there are and how they respond/adapt to various kinds of stresses, the neurological components of strength. It explains how to create your own routine that fits exactly your current skill and fitness level, including skill work, stretching, and strength training. It explains basics of programming and how to deal with plateaus (->periodization). It has a huge chapter on injury prevention and health management. Then it has a large collection of exercises, from basic pullups and Wall Handstands to more advanced stuff like planches, iron crosses, mannas and so on. Exercises are structured in groups, and the author provides progression charts for each group.
The cons: This book is only about the upper body (which is what gymnasts mainly care about). And an index is missing for looking things up.