They're worthless, sadly. You can make a free library-type thing, but nobody wants them.

The best use is to glue the pages together (one set of about 20 with the cover, one set of 20 with the back cover, and then the rest). Put it on a bench/vice and use a jigsaw to cut open the center portion, and then glue the back section to the hole you now have, and now you have a book you can hide something in.

Or just burn them.