That seller at the Portland book sale taught me to always check the last page, and it saved me $60
I was at the big used book sale in Portland last month digging through the $2 paperbacks when a guy next to me noticed I was about to buy a beat up copy of a Vonnegut novel. He asked if he could see it, flipped to the last page, and pointed at a stamped "REVIEW COPY" mark I had totally missed. He explained that book club editions and ex-library copies get mixed in with true first printings all the time, and that one stamp meant my $2 find was actually worth around $60 to the right buyer. I ended up buying it and selling it a week later for $55, which covered my whole haul that day. Now I check the copyright page and last page on every single book before I pay. Has anyone else had a stranger at a sale point out something you completely overlooked?