FWIW my experiences with MathAcademy roughly overlap OP’s: it’s really hard work and adult life seriously interferes with making speedy progress (notice their own success stories are with teenagers who can devote hours upon hours on racing through the - very good - curriculum).

They say 1 point is equivalent to 1 minute of work and that you should earn at least 45 points a day. Well, for me 1 point is nowhere near 1 minute of work: I’m sloppy and sometimes downright stupid so it’s 1,5 minutes at best and often much, much more.

Banging your head against a wall every day for more than an hour (sometimes much more) just to get to what they consider to be the minimum of 45 points is no fun, and probably even counterproductive. I managed to keep it up for four months and made reasonable progress during that time (on getting back to where I was at the end of High School, 30 years ago) but it also burnt me out. I’ve now scaled it back to 30 minutes (not points!) a day. As a result my progress is now glacial.

Also, they’re very much of the “just do lots of problems and you’ll learn mathematic concepts and principles by osmosis” school of math instruction. For me I had to buy a textbook to get some extra explanation.

The good thing is that the problems seem well thought out and the spaced repetition system definitely works (for me, anyway).

I’m going to keep it up, because I have enough disposable income to afford it (though it is much too expensive for what it is) and I really want to bring my math skills up to a level where I can follow along the math in ML papers (and also because math, it turns out, is kind of elegant and interesting). I could go the self-study route, but then I’d have to spend time and effort guiding myself and figuring out what it is I needed to work on. If nothing else, MathAcademy is good at taking care of this for you so you can focus on the math itself.

Any pointers on useful textbooks in this space? I seem to have difficulties finding one that is at the right level (not too easy, not too hard) or that provides a way to gauge your level and start accordingly at a later chapter or whatever.

Yeah, I only have a goal of 25 points a day, Monday through Saturday, and I still usually take more than half an hour (though usually less than an hour) per day.

I actually feel that 25 points may be a bad choice as it makes me spend too much energy picking lessons that will barely add up to 25 so I can be done with my daily. Probably causes me to review or whatever when maybe I don't need to?