selling used books: classic or frustrating dud?

Well, it depends. By and large, it is an experience superior to the sale of records and clothing in every way. Someone will always complain about vinyl, I would only sell it if I were absolutely certain of the condition and worth. Ditto for books. Otherwise the books can easily be donated to someone ... records - I'd sell low if I were not sure - people might complain to you about your ludicrously low price but it's a learning experience. As with books those things can take a lot of space.

Selling records or clothes is stressful - books, not at all, but perhaps it's because I also spent a good chunk of my adult life buying them.

Info on your book is much easier to find, prices more stable. You'd be surprised at how many $200 and $300 books you can sell if you are branching beyond novels! I sold my dad's law and math books and netted about $600!! Art and architecture is a good investment, too - and what I like is that you are certain of the item's worth, whereas really expensive vinyl can be - musically speaking - SHIT.