In the States, the act of copyrighting a book makes it eligible to be stored in the Library of Congress. This more-or-less guarantees its immortality.

In the United States, writing a book makes it copyrighted. It's impossible to not. You can then grant it to the public domain, but it was still copyrighted at conception.

Copyright here has two different meanings: the default copyright which applies to all works from the moment of creation, and registered copyright, which the above post is referring to. Registering a copyright includes depositing a copy of the work with the LoC.

No, copyright doesn't have two different meanings. He was talking about registering his copyright on a book, which is what does what he's talking about, not copyright.

For legal purposes, there is very much a difference between a default copyright and a registered copyright. One is actionable and allows for damages without proof of injury, the other is not actionable (in the U.S., though EU copyright law differs).

Yes, registration does makes getting damages easier.

However, that's not the point, the point is that the poster who I originally replied to thinks copyright is copyright registration. Copyright is granted upon creation in the US.

Registration is something you can do with a copyrighted work to make damages easier to gain.

While the state grants a car title and a car registration, they're different things. Same with copyright.

Copyright before the modern era required eventual registration to be valid, and I believe that's where much of current misunderstanding on the topic comes from:

http://copyright.cornell.edu/resources/publicdomain.cfm

Wait, if a book isn't copyrighted, it's not eligible for inclusion in the LoC? How does that make any sense at all?

The act of copyrighting a book includes depositing a copy with the Library of Congress. The LoC used to accept all submissions; now it only accepts submissions filed pursuant to a copyright.

Yeah, that's false.

Does it matter if it sticks around forever if it isn't being read?

How would you determine that a book isn't being read?

Well if the author/ copyright holder stops publishing the book and no one else is allowed to it is going to quickly fade into irrelevance, even though there are a few copies out there being kept safe indefinitely. Whereas if the book is in the public domain, the quality of the book and popularity will decide whether it continues to be read, rather than anything artificial.

Is very hard to find a large audience for a novel without some level of commercial publishing being involved and they will want standard copyright terms.

An interesting exception to this is in the comic book industry where there are a few successful self publishers.