Mind of Steel Handbook is a rulebook that teaches you 12 universal rules of mental strength and how to implement them into your life with specific exercises and examples.
There are 12 chapters, one for each rule. Each rule describes:
How it helps you build mental strength
Problems that happen if you break it
Simple, actionable methods to implement it in your life
Real-life examples
These rules are based on various philosophies (like stoicism and rationalism), scientific research into the human mind, and real-life examples and situations.
In others words: Backed by science, tested in the real world, and explained in terms you will understand.
More details: https://themindofsteel.com/books/mind-of-steel-handbook/