I'm a bit tight on bookshelf space so I'm taking the less important stuff and boxing it up.

I had four shelves of World of Darkness -- Vampire, Werewolf and Mage -- all pre nWoD plus the 20th Anniversary core books. I decided that if I ever run these I'm just using GURPS and the 20th Anniversary core plus adventures (chronicles I think they're called in WoD). There are actually very few adventure books and some sourcebooks have adventures but they needed to be at least 20 pages to be included. After the culling I went from almost four shelves to the better part of one shelf.

I have two shelves of Call of Cthulhu material and CoC has more adventure books than WoD. Still, remove the pure sourcebooks, all the books outside of the 1920's (except for Beyond the Mountains of Madness set in the 1930's) -- CoC has good support for Cthulhu Now and remarkably Ancient Rome when I stopped buying stuff. Still too much so I'm only keeping campaigns and the Goodman Games CoC adventures line. That brings it down to about half a shelf and this including the 1st edition KS stuff (I will run with GURPS + 1st edition).