Right now, books published in the U.S. before 1924 are in the public domain. This means they are publicly owned and everyone can use and copy them. But there’s a loophole in copyright law which gives up to 75% of books published between 1923 and 1964 secret public domain status. It’s hard to figure out which ones they are, so a group of libraries, archivists, and volunteers are finding these public domain books, scanning them, and uploading them to the internet.

Richardson notes that much of that heavy lifting is being done by volunteers at organizations like Project Gutenberg, a nonprofit effort to digitize and archive cultural works. These volunteers are tasked with locating a copy of the book in question, scanning it, proofing it, then putting out HTML and plain-text editions.