From The Atlantic:
Because of the strange distortions of copyright protection, there are twice as many newly published books available on Amazon from 1850 as there are from 1950.
The above chart shows a distribution of 2500 newly printed fiction books selected at random from Amazon’s warehouses. What’s so crazy is that there are just as many from the last decade as from the decade between 1910 and 1920. Why? Because beginning in 1923, most titles are copyrighted. Books from before 1923 tend to be in the public domain, and the result is that Amazon carries them — lots of them. The chart comes from University of Illinois law professor Paul Heald.
Link to the rest at The Atlantic and thanks to Abel for the tip.
Passive Guy speculates that the answer to most of these vanished books is that the rights to those books have fallen into a crack between the original publishers on the one hand and authors and authors’ heirs on the other.
Since the 1930′s publishing has undergone a massive consolidation and most of the publishers that existed from the 30′s-50′s have disappeared or been acquired and re-acquired and re-acquired yet again. Tracking down old publishing contracts may be next to impossible under those circumstances.
Likewise, many of the authors who published during that era are deceased. If royalty payments on their books ceased prior to their death, the heirs may only the vaguest idea that they have inherited copyrights to these works. If you throw pen names into the mix, things become really sticky.
As Google discovered, however, if you decide to make old books available for the general public to read, you walk into a mine field.
Out of 100 books published in 1930, it is likely that 99 could be republished with no objection from anyone. However, the potential consequences of a copyright violation claim on the 100th book would make the entire undertaking too dangerous to pursue on either a commercial or non-profit basis.