Hi Ed – we do mention GitHub updater as a potential way to keep Pressbooks plugins and themes up to date in our readme, that is true. I found this: Pressbooks-book. My understanding is that GitHub updater looks for tagged updates and allows you to update when they become available. I checked McLuhan and our latest tagged version is 2.17.0 and the style.css file lists the version as 2.17.0 in master branch as well: pressbooks-book/style.css at 0b72971f9c3807e2db82b197191f3863ba02b44e · pressbooks/pressbooks-book · GitHub (see tagged commit: pressbooks-book/style.css at 0b72971f9c3807e2db82b197191f3863ba02b44e · pressbooks/pressbooks-book · GitHub). I checked Aldine and see that the style.css in master is also 1.14.0: pressbooks-aldine/style.css at 056698550d0edc8825feb1e46e782ae754f04115 · pressbooks/pressbooks-aldine · GitHub. This leads me to believe that our releases are not broken, but that something might be going wrong with your particular use of GitHub updater, which is much harder for us to help you debug. Could something like this: Theme update errors - #11 by SteelWagstaff be helpful? If not, I’d probably recommend checking the GitHub updater support forums. Maybe start here? Usage – Git Updater
If you learn something there that reinforces your sense that this is a Pressbooks release problem, let us know and we’ll try to fix it!