Sometimes I'll see something I already have and wonder if the copy I own is as good as the copy in front of me. It's not easy finding older books and records in pristine condition, but it happens. With records, there's always the added attraction of liner notes or inserts. With books, you never what someone will stuff between the pages. Newspaper clippings and letters are fairly common, but I've also found photographs, check stubs, and plane tickets.
The other day, I found this Elektra folk sampler from 1958.
I paid for the books and peeled off all the Goodwill stickers while I sat in the parking lot. Then I whispered "score" and drove away.