You must be doing rotations, or else you wouldn't have all this time.
Physiology of Sport and Exercise by Wilmore, Costill, and Kenney
Exercise Physiology: Energy, Nutrition, and Human Performance by McArdle, Katch, and Katch
Exercise Physiology: Human Bioenergetics and Its Applications by Brooks, Fahey, and Baldwin
I'd start with one of the first two before going onto the third book. Plus, the third book is going to come out with a new edition.
This is what Fahey had to say about these books and their authors:
While the basic information in these books stays the same between editions,
authors add new developments each time. The changes in our field have been
astounding. If you can afford it, buy the new edition.
As a sidelight, many of the textbook authors are professionally related. Jack
Wilmore was one of my professors at Berkeley, Bill McArdle was George Brooks'
undergraduate mentor at Queens College in New York, Vic Katch was my office mate
at Berkeley, and Frank Katch (also a Berkeley guy) is a golfing buddy and
colleague on several projects. All of us have been friends since the 1960s. The
major differences between the texts are the target audience and the interests
and expertise of the authors. George Brooks is one of the premier exercise
biochemists in the world, so his book emphasizes biochemistry. Wilmore and
Costill are more practically oriented and interested in public health, which is
reflected in their text. McArdle and the Katch brothers have an excellent
background in nutrition and general physiology, so their book is a good choice
for most undergraduate courses.
The leading textbooks feed off each other. Publishers evaluate their competitors
and include missing information in the next edition. However, George Brooks is
brilliant and has an incredible grasp of exercise biochemistry. The nuances he
adds to our textbook are difficult to duplicate.
Cal State University, Chico