Books in the public domain.

It is surprising what you can get. I did think about subscribing to Amazon's new service, but I don't think it is worth it for me at the moment.

Publication 30 years in not old enough. At Project Gutenberg, the law is clearly laid out:

www.gutenberg.org/wiki/Gutenberg:Copyright_How-To#Definitions

British law states that, author's copyright is the lifetime of the author and 70 years thereafter. Those regulations are retrospective; they caught up books that had previously been out of copyright: they extended the copyright period for all works which were then still in copyright, and (controversially) revived the lapsed copyright of all authors who had died in the previous 70 years. This legislation was brought in in 1995 and brings it very closely in line with American legislation. Paul Colinvaux only died this year, and so, unless he released it under something like Creative Commons, it will not be out of copyright until 2086, 70 years after his death.

Copyright is something that is mostly pushed by powers that be. For a while, people worried what would happen when the Lord Of the Rings came into the public domain, things like that. People who had certain rights would lose them, and there would be a free-for-all. My personal view is that copyright should stay with the holder and estate, for a certain period determined, not by the life or death of the author, but by the date of publication of the book (publication plus 30 years, say), with a secondary proviso that future copies are not allowed modification. You could not, for example decide that you could change the end of Harry Potter so that Harry marries Luna Lovegood, Hermione marries Draco Malfoy, or a Lord of the rings in which ends with Frodo and Sam falling in to Mount Doom, or Galadriel taking the Ring.

You are right, though. Some authors do put their writings in the public domain, some do it just to get their work out there, not in the sense that you are free to do what you like with it, but that you do not have to pay to get it, and you must keep it in the exact form that you found it, with no additions or deletions. (This is what is done by Project Gutenberg, but a few publishers just ignore this, and make it their own.

Project Gutenberg have divided their catalogue into a number of sections, here is their section for Detective Stories. It is curious to note that the works of Agatha Christie started to come out, but, when copyright laws changed, they suddenly stopped appearing, and won't appear in large numbers for a while.

www.gutenberg.org/wiki/Detective_Fiction_(Bookshelf)

The full set of categories can be found here:

www.gutenberg.org/wiki/Category:Bookshelf

I had completely forgotten about this great resource for people who want to read some serious books.

www.bartleby.com/

Among their more famous collections is this:

The Harvard Classics - The Shelf of Fiction

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