Book sales always pull me in two directions. On one hand, there are often books there which I would love to buy.
On the other hand, book sales have been my introduction to previously unknown (to me) authors or subjects -- and if I buy the book, I'm denying that opportunity to how many others?
Its all the harder when, like now, it is a library selling its collection.
(those books not sold by 2pm today, were discounted to "anything you can fit in a grocery bag, is $2"...anything left unsold by 3pm would be sold for a lump sum to a single buyer - nothing would go back on the shelves)