Baron Wulfhere of Stonemarche is my first Heavy List mentor. Before I attended my first practice, he encouraged me to pick up a copy of The Armored Rose, a book written by one of the first Lady Knights of the Society. If you are (or are planning to train) a lady, a person assigned female at birth, or a person transitioning to female, this book is invaluable. It covers body mechanics, societal and gender issues, and armoring the female form as compared to the male.
The Armored Rose by Tobi Beck can be found on Amazon.
Also on the recommended reading list are The Book of Five Rings, The Art of War, Hagakure, and Clausewitz on Strategy.
Clausewitz on Strategy