There are a lot of books about developing better cardio.
And I've read most of them.
But the best book on building better cardio I've found is Ultimate MMA Conditioning by Joel Jamieson.
For a few reasons:
Reason #1: It breaks down the exercise physiology of the 3x energy systems in the body in an easy-to-understand way
Reason #2: It outlines how to assess your starting point for cardio easily
Reason #3: It gives multiple training methods to develop each of the 3x energy systems
Reason #4: It shares an example 8-week plan to develop your cardio
Reason #5: It's written by a true expert who's worked some of the top athletes that are praised for the great cardio endurance.
If you are at all interested in improving your cardio, I can't recommend this book enough.
(And if you've read it, do you agree? What other book would you recommend for beginners?)