Newer and hardback mean they are aiming at a collection of books that can hold up to circulating for a while and that will be current for the readers to use. So I'd hazard a guess that your old 1968 (or even 1998) Encyclopedia Britannica is out of date. But textbooks you used in recent classes, fiction books and nonfiction books, literature, How-to and Job training books would all be helpful.

The need for escapist and pleasure reading will also pressing, so again, I'd guess that your recent popular hardcover mysteries and thrillers and romance and general interest novels will also be suitable. And many libraries do have circulating popular paperbacks.

Don't forget hardcover children's books. Dr. Seuss, Newberry and Caldecott books, many others that you know are good children's books will work. Hardcover is almost a MUST for children's books at a library. They get a lot of rough treatment.

SRS