Thanks to horribly egregious copyright legislation, books published from the late sixties onward are typically under copyright for 100 years, meaning that someone besides the author is charged with administering rights. That person is usually completely ignorant of book publishing and the content of the book or why it matters. All he wants is money that is not there. More often than not, this person will refuse to make a deal. And book [sic] stays out of print, for the rest of our lifetimes at least.
This is what copyright extensions have amounted to: great impediments to printing books and preserving literary legacies. Already, provisions of the law have burned more books than most despots in human history. And this has only just begun. We are going to be seeing this nonsense for another 100 years at least.
Truth be told, Tucker may well be understating the harm of lengthy copyright terms. Even books that it would not be economical in the least to bring back into print could be made accessible online at Google Book Search, Archive.org, or a similar service.
On the topic of intellectual property generally, I recommend this excellent EconTalk podcast with Michele Boldrin, as well as Boldrin and David K. Levine’s thought-provoking book, Against Intellectual Monopoly.