A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2021 Sep 6, 08:48 -0700
John Clements, you wrote:
"Anyhow, it turns out that there are a LOT of books in this category. Also, unfortunately, nearly all of them are newer than 1926, which I believe is the current threshold for copyright expiration in most cases"
Don't forget hathitrust.org. Here's the advanced search function. Many of their books are newer even though they're still under some formal copyright protection. I've read books published as recently as the 1990s at hathitrust (this is pronounced like "hottie trust" btw). Though they don't allow full downloads of books without an institutional account, you can download pages in batches and put them together offline. Or just read directly online.
And archive.org also bends copyright law. Many titles from defunct publishers are available at archive.org. Their authors or heirs of the authors could claim copyright and have the books removed, but this seems to be rare.