The seller and law say you own the book but you don't own the content of the book. That is, you are free to read the book as many times as you like, you aren't free to start printing out and distributing copies of the book as "backup" for all your friends and family.

The laws around DVDs are the same. You have a right to access and view the contents of the DVD. You don't have a right to make copies of the dvd.

I'd also point out products like cheap paperbacks which obliterate themselves after 4 or 5 reads.

Don't get me wrong, I'm all for some good reforms and regulations around copyrights and media access, especially in the digital age. I just think it's a little bit ridiculous to expect purchased media to never degrade.

Buying a book doesn't give you any more rights or privileges that buying a dvd. Although I guess it's a lot easier to take a book and give all your favorite people a portion of it. You're paying for the physical object and have a license to read it or view it, but not to copy it (other than what fair use provides). Many books have an explicit statement of this on the copyright page.