There are people who are willing to buyback old and used books from you. Simply visit their site and package and courier it to them and you will get your money after successful delivery.
You need to know the ISBN of your book to qualify for the buyback. The number beside the vertical dark coded lines on back cover of most books.
The book could be in used or new condition and your quote will depend on the same.
Enjoy releasing the dust accumalated on your old and torn books eating out your library space. Get some fresh air in.