Kind of reminds me of when I picked up a copy of Ignition! (https://www.amazon.com/Ignition-informal-history-liquid-prop...) at a used bookstore for $5. I definitely got my money's worth out of the read, and I was quite surprised years later when I heard it was very rare. I still haven't sold it.
Me too. I always borrow my books, but I don't want to sell them. I will try to keep them. I'm always returning to books I've read when I need some advice.