How do I find the most profitable books at a library book sale?

This is very much opinionated so I will share what has worked for me.  At the beginning of a sale will be a frenzy if it’s a well known book sale.  Avoid fiction books until the very end.  You’ll want to look for what you’re more likely to find multiple very profitable books.  My first category I look for at a book sale are College Textbooks.  They often sell for a high dollar amount and they sell quickly during textbook season, which tends to be at the beginning of the college semesters(August and January). You will often find success with other non-fiction categories like Business, Law, Social Sciences, Economics, Theology, Information Technology, Art, Military History, Music, Automotive, etc.  The more niche the book is, the more likely that it’s going to be a winner for you.  If you do end up going to the fiction section your main focus should be graphic novels.