But a copyright loophole means that up to 75 percent of books published between 1923 to 1964 are secretly in the public domain, meaning they are free to read and copy. The problem is determining which books these are, due to archaic copyright registration systems and convoluted and shifting copyright law.
As such, a coalition of libraries, volunteers, and archivists have been working overtime to identify which titles are in the public domain, digitize them, then upload them to the internet. At the heart of the effort has been the New York Public Library, which recently documented why the entire process is important, but a bit of a pain.
—Karl Bode, in “Libraries and Archivists Are Scanning and Uploading Books That Are Secretly in the Public Domain”