30 Books Mattis Thinks Every Good Leader Needs To Read

Great list but I would add Plutarch. The character of soldiers in war and peace should be known by the examples. I would also recommend Greek and Latin military history.

I must be doing something right, I've already read eleven of those.
I would add several, but I will make two recommendations:
1. "On War" by Carl Von Clausewitz
2. "The Savage Wars of Peace" by Max Boot

The latter is a must-read for anyone involved in current low/mid-intensity conflicts.

I think "the west point way of leadership" was a fantastic read