Book purging is an occupation hazard around here.

Tomes pile up in
corners of the office and in hidden bookshelves in the attic. What if I
need a footnote in the future? Steve blows through a 500 page biography
of Hilter or Marcus Aurelius every month or so. The shelves of Hilter biographies in the dining room frequently freak out new dinner guests, but it could be so much worse. Without editing, there would be no room to eat in our dining room. We need to regularly purge the shelves in order to avoid an untimely death.

Here's some expert advice on books that can you live without.