This is THE book on adaptations happening in your body when you train:
This is a good book to read about the way our body adapts to stress in general:
This book has a lot about everything, but very little on the cardiovascular system:
If you want to learn more about the cardiovascular system, you could read any of the top 3 Exercise Physiology textbooks (McArdle & Katch, Brooks & Fahey, Wilmore & Costill). Brooks & Fahey is supposed to be the best and most advanced of the three, as it includes a lot of biochemistry.
Besides Why Zebras Don't Get Ulcers, those are all advanced level books. I suggest you start by reading "The Runner's Body: How the Latest Exercise Science Can Help You Run Stronger, Longer, and Faster." The authors are the guys who run the Science of Sport blog, and it is fairly easy reading. I also think you'd do well by reading Joel Jamieson's "Ultimate MMA Conditioning" book. It does a good job of dumbing down basic physiology, and it gives a good application of the block training model.
(And, I have not read most of these books, but I own many of them. I do not have a science background yet, so I'm holding off on reading some of these for if/when I have the chance in the future. I have a bad habit of buying books I know I will not read right away. I have about 100 books saved in my Amazon Shopping Cart...