The reserve was not met. Reserve auctions should be avoided. They are not appreciated by bidders. The only time they are appropriate is for very high value items where the seller is afraid of scaring away bidders with the actual cost. Even then, they aren't a good idea.
Many bidders refuse to take part in auctions that carry a reserve on principle.
Try different titles to reach different groups of bidders. And when you do sell a book, contact the buyer by e-mail immediately, conduct the transaction in a friendly manner, and send out the book as soon as you receive payment. Also remember to leave the buyer feedback. It is an ingenious system that keeps everyone honest and encourages the best behavior. When you receive payment for a book, you can go to the web page for that auction and leave a message about the buyer.