When a book's copyright expires, it enters the "public domain," which means the title is no longer protected by intellectual property laws and is legal for anyone to disseminate without permission.  Most works enter the public domain because of old age.  Their copyrights were simply not renewed.  Click here to read more about Public Domain.

Before you spend $14.99 on that copy of Moby Dick, consult one of these free e-book respositories.  Many great works of the literary canon can now be read for free online.