What is a rare edition book?

Rare editions can often be books that have been printed with mistakes in places etc. I know that one of the Harry Potter's was printed wonky or wrong somewhere, it's likely they could be worth something, because people often enjoy mistakes as they are quite rare too. Rare editions can also be first editions that had few printed. If your really interested in finding out about your book i suggest you visit an antique shop, they might be able to tell you something about it, or specialist antique shops.