Best place to sell a book

If it's a book of pretty decent value, you could list it on Facebook marketplace or join some signed books Facebook groups. Things sell pretty easy there and you'll avoid eBay fees. A book store most likely won't give you close to market value because they obviously want/need to make a profit on it.

Do you know the going rate for the book? I'd just make sure you know that so you don't undersell yourself or over price it and it never sells.

Harry Potter and the Deathly Hallows, first edition, signed by J.K Rowling. Happened across it at a thrift store.

stumbling across signed books and other cool one-offs at thrift stores and used book stores is one of life's little pleasures for me. i've never found anything super valuable or anything, but i've got a book signed by Ollie North and another by David Hackworth which i think are both super cool. i also found Chuck Yager's autobiography one day with a numbered sticker in it saying that it accompanied him on some test flight or something in some specific platform. i dont think any of them are worth anything crazy, but they're cool to me and i like having them in my collection. i also found a first edition of Silence of the Lambs in a thrift store one day for like $5.