Book collecting can be an exciting hobby and perhaps even an investment.  You can purchase early edition books relatively cheap.  First editions and rare books maintain and increase in value over time making book collecting a good investment.  With the help of online market places, finding books to complete your set is relatively easy.  As you progress in your collecting, search for those rare sets and first editions.  Autographed books also can be of high value but be careful.  There are many fakes out there.  Do your homework when purchasing high end books, especially online.  Get several photos and verify condition.  Ask if there is a money back guarantee if not satisfied.  Use online resources such as the Advanced Book Exchange.  This can be a fun and profitable hobby if you are smart in your collecting.