My take was that this book was REALLY comprehensive and covered every aspect of conditioning you can imagine. Major chapters include:
-warm-up and flexibility training (includes all the major stretches)
-agility and footwork (specific drills to improve your footwork)
-speed and quickness (more drills to increase your speediness)
-core training (a lot of tennis moves depend on a strong trunk)
-strength and power training (exercises to increase your upper and lower body strength)
-aerobic training (ways to increase your endurance)
Also included, a short section on injury prevention - only a page and a half on tennis elbow though (suggest Treat Your Own Tennis Elbow for more on that).
Just a ton of information here and I can't see anybody who plays tennis reading this book and not coming away with at least a few nuggets of wisdom. Get this book if you want to get in better physical shape to play tennis or if you're a coach and want more training tips and ideas.