Let's see... .that would be about 2/3 of my collection.
I own a lot of rpg books. I even own about 70 books of D&D 3rd edition.
I've always bought many rpg-books just for 'reading'. I only have time for so many systems/different worlds, but they make great idea-pool. I haven't even read all of them. I will someday, of course.
To add to that I've suffered for about four years unability to concentrate into anything non-interactive, and that makes reading books really hard. Hah. but I am slowly getting my normal mind-set back, I don't fast-forward all the movies and such anymore.
Ok, then there rpg-stuff I read/use partially. Life FR-stuff. I have severe Forgotten Realms allergy, but those books contain very interesting and usable material besides all-those-things-I-can't-stand.
I use many monsters and spells from Rokugan books, but I don't use that world itself.
Despite the fact that I own that many 3rd edition books, I actually use most of them, except for low-level modules I happened to buy. They are just too lacking of ideas worth converting to our high level games.
Oh, yes, there is one exception. I just didn't manage to read that Kalamar HC book. It was soooo boringly written. I've heard it contains interesting ideas (hidden to me), but the manner that book is written, lacks totally the spark that lightens my imagination.
