There are certain types of books that I more or less assume all readers read. (Novels, for example.)
But then there are books that only YOU read. Instructional manuals for fly-fishing. How-to books for spinning yarn. How to cook the perfect souffle. Rebuilding car engines in three easy steps. Dog training for dummies. Rewiring your house without electrocuting yourself. Tips on how to build a NASCAR course in your backyard. Stuff like that.
What niche books do YOU read?
I've read books on art, martial arts, diet, and weightlifting. For most of these books, I borrow from the library.
On the art front, I love Burne Hogarth's Dynamic Figure Drawing and Betty Edwards' Drawing on the Right Side of the Brain. I keep telling myself to get copies of both books but I keep forgetting them since I haven't done anything artistic recently. As for other books, I own Chinese Gung Fu: The Philosophical Art of Self Defense by Bruce Lee and Nunchaku: Karate Weapon of Self-Defense by Fumio Demura. My nunchaku has been on display collecting dust for many months now.
I've also read Hand-Made Books: An Introduction to Bookbinding by Rob Shepherd and skimmed throught Bookbinding & Conservation by Hand: A Working Guide by Laura S. Young. The second one was too technical and in depth for what I needed.