Well my wife just went out and bought three new bookshelves about 2 months ago. Those are pretty full with stuff, lower shelves are kids books for my daughter, then our adult picture books(archetecture, cars, gardens, fish, etc) then an area of antique books, and other neat books we like to have out on display...
I'm not allowed to display my fantasy novels because I strictly and only, to the point of religously buy paper back. The better half says they look too beat up by the time I'm done with them

The fantasy stays in my closet; four 5ft. wide shelves each double deep with more laying on top and a few boxes on the floor...
Then I still have another 7-8 boxes back at the parents house... I'm proud to say that I live with out a 'To Read' pile. there's a few books I'll never read, but I buy-as-needed, usualy a day or two before I'm going to finish the current book.

sorry, I'm not going to estimate the total #.
Why'd you make me think of this? Now I'm going to start to do the math and see how many thousands of dollars I've spent on my habbit...
-Silas