Aww I get it Max! Even if it was a parent (good parenting though, be responsible with what you take and don't take more than you need) I know I'd personally feel guilty about holding onto too many too long.
Maybe you can put a sign on the library that says something like, these books are here for a short visit or their next forever home. Enjoy!
Or it doesn't have to be cute but I like cute cuz little libraries are.