Books are one of the easiest things to pack but can be one of the hardest to pack correctly.
Even though a book is non breakable it still needs to be packed as if it could break. When you sell a book you may or may not know its true value. The buyer may be a dealer who has a long standing order for that book, a collector needing it for their collection or simply someone wanting a reminder of their childhood. Because of that you need to treat every book as if it were very precious. With books condition is paramount.