It's available on amazon in a hard cover edition. So someone still owns the copyright to it. 

Not necessarily. Someone might own the copyright to that printed hard cover edition, but not to the content within in. Think about the fact that people still print and sell Shakespeare's work, even though it's freely available in a horde of places.

Shakespeare's work is "out of Copyright" because it's three-hundred years old... Copyright has nothing do with someone selling a "hard cover edition," as long as the Copyright Holder has authorized them to create and sell such an edition. However, if the Copyright has expired, as is the case in the above example, than anyone can reproduce it. However, in the case above, the creator of the product owns  the entire product, including what is between the covers, but can not claim Copyright on the actual contents.

Copyright is there to protect the rights of creators and to encourage further creation by making it possible for creators to profit from their work. However, it does not last forever. The reason that Copyright expires is that not only should the creator profit from their work, but that work should also be able to benefit everyone. Oh, and it's also extremely difficult to justify protection in perpetuity.. There are also "Acceptable Use" issues that Copyright must obey, in order for society to receive the most benefit from the work of its members. (Usually targeted towards intellectual discussion of copyrighted works, for educational purposes.)