Booklovers of the world unite!
At any rate, make sure to check out College and University libraries, they frequently have very limited space, and are constantly buying new books. Something has to give, and they usually have 2 or 3 sales a year, if not a rolling garage sale.
I've picked up some incredible volumes over the years at my college...a notable one, although I forget the details, because it's at my parent's house; Plato's Republic, bound in the 18th century....a 20 volume set of WW1 historical documents and letters by notable figures of the times, illustrated with hand-coloured lith's, etc.
Not to mention the piles and piles of art-books, atlases, and encyclopedias.
My wife won't let me buy any more books (at least by the ton) because we have so damn many of them, and it almost fills a moving truck just for the books!
Not to mention that I picked up stacks and stacks of books while I studied in Europe a few years ago, and they are at my wife's parents' house in Poland.
And I'm only 27....I shudder to think what things will be like when I'm old.
Edit: I forgot to mention that my name is Lawrence, and several years ago I was in Jordan, at a place the name of which I forget....anyway, it was one of T.E. Lawrence's staging grounds. Now it's largely ruins, but his office is still standing, with a large glassless window. I have a picture somewhere of me peering out the window of Lawrence's office....the friend that took it called it, appropriately "Lawrence's Office."