i used to have a couple of hundred or so focusing on military history. I enjoyed having them and would reread something occasionally. Then I moved to a smaller house and decided to donate them to the local library. I thought they would make a good addition to their history section. Instead they sold them for $.50 each.
I probably have about 20 books now. When it creeps up to 25-30 I take them to the library - in a different town.