Many of these books contain strong language or graphic pictures due to the nature of their subject. I do not support all beliefs presented in the works below, but each work has wisdom within it.
Leadership:
The Mission, The Men, and Me by Pete Blaber
Medical:
30-Second Anatomy by Judith Barbaro-Brown
PHTLS Prehospital Trauma Life Support Textbook by NAEMT
12-Lead ECG for Acute and Critical Care Providers by Bob Page
Rapid Interpretation of EKG’s by Dale Dubin
Philosophy & Problem solving:
Left of Bang by Jason A. Riley and Patrick Van Horne
The Art of War by Sun Tzu
Algorithms to Live By by Brian Christian and Thomas L. Griffiths
Boyd by Robert Coram
The Way of Zen by Alan Watts
Zen And the Art of Happiness by Chris Prentiss
The Back of the Napkin by Dan Roam
Miscellaneous:
The Little Prince by Antoine de Saint-Exupéry
Roadside Picnic by Arkady Strugatsky and Boris Strugatsky
Get Tough! by William E. Fairbairn