It was mostly made (relatively) easy by the fact that I was moving lots of books anyway, and it therefore didn't add much time or effort to periodically say "I'll never want that again" and put it in a different pile. As for massiveness of the piles... well, I reckon that the ~130 books in that list constitute more than 5%, but less than 10% of the number in this room. And this room probably contains at least 2/3 (probably over 3/4) of the books in the house (by number; not necessarily by mass, since the cooking, gardening, etc, books that are stored elsewhere tend to be both considerably bigger than even a large-format paperback and somewhat denser because they're printed on better paper).