[CRConrad]

> Copyright blocks most derivative work (with a few exceptionns like parodies), but also blocks verbatim unauthorized copies.

Maybe verbatim unauthorized copies is all it should block? Hey, it's right there in the name, isn't it -- Copyright? It's not called "parodyright" or "derivativeright"...

[irtigor]

Translations, revised editions (to fix typos, add examples or change the bookcover) and adaptations to other media formats are examples of derivative works, so copyright law would be pretty useless without that kind of protection.