I once read a true story of a crew of rescuers searching for a lost hiker. After hours of searching, they finally found the man’s body, leaning against a tree, surrounded by the contents of his well-equipped backpack. He had everything he needed to survive, yet must have lacked the skills to use them for his survival.
Likewise, your home library may be filled with survival manuals of all kinds, but which of those will be most user-friendly and practical should you ever need that knowledge in a crisis?