Besides matchbooks I also collected clear glass oil lamps for a brief period of time. Originally I just wanted one oil lamp that looked old, to use when the power went out. Then I got hooked. Had to stop when there was no more place to put them. Half of the collection. Nothing valuable. Just each one with something a little unique about it.
Aside from books, I've also collected owls carved from various materials -- crystal, jade, wood, soapstone, etc.