
Build Your Own Lisp, by Daniel Holden. This is an often cited classic with a lot of precious concepts explained in detail. It can be read for free online. But this is an opportunity to reward them for it. (Yes, I do own a purchased copy).
Ansible for DevOps by Jeff Geerling. Already mentioned by the sibling commenter.
There a lot more on my wishlist. All of them are competitively priced at 10 to 15$ each.
I have heard someone trying this approach with music albums and succeeding at it. The album is more likely to go viral due to the easiness in sharing, while you'll always find consumers who volunteer to pay you. While the returns per copy is low, the large number of copies means that your profits may be higher than if it were DRM-encumbered. Musicians may also like the fact that there are no powerful middlemen that they have to contend with. In fact, this is what YouTube creators already do when they choose alternative monetization paths like Patreon.
What's really needed is for people to support and encourage this model and such creators. We used to earlier blame them saying that people choose convenience and short term savings over long term market health. But that's no longer applicable. People are so fed up with being exploited under consumerism that they've started boycotting these big players to regain their independence and self sufficiency. The real issue preventing open digital markets is just the lack of awareness of their existence. This message has to be spread somehow.