The Single Founder Handbook, by Mike Taber, is an interesting book focused on simple startups, not the kind where you try to get funding. It is also mostly about software developers.
I've been selling software online for 20 years (see my site for most of my software), and this was still full of interesting ideas.
In particular, I liked this version of how to generate and validate product ideas, and the chapter on how to outsource.
I also thought there were some useful insights in Routine Maintenance section, about how health, personal retreats, mastermind groups and the like.
I got the simplest version – just the ebook. I didn't see the other assets as particularly useful for the price.
Overall, pretty good, and I can recommend the basic version.