I voted for the over 25% option, but my figure would probably be much higher. I'm pretty easy going with all my belongings, really, and giving them away comes easily. I usually end up giving away the things I enjoy the most, provided I know the recipient wants/would enjoy it, and I do enjoy books!
Also, ever since living in dorm rooms for 3 years with some awful roomies, I've become quite averse to clutter, and keep an eye out for reasons to get rid of things. I've moved a lot in the last few years too, and I get rid of a lot of things then too, because there's not many things I love enough to lug up and down stairs a lot.
Right now I have 2 sizeable boxes ready to be taken to the library and Goodwill. Haha.
That said, there are definitely some books I will always keep, or, you'll at least have to pry them from my cold, dead hands to get at them.
