cstross, About Amazon's decline in recent months: I have an Amazon account I use ONLY for buying ebooks. Nothing else, ever, going back over a decade.
My recommendations page in that account now contains no ebooks, only products from categories I never purchase, like lawnmowers (I don't have a garden) and dresses (I'm a boring cis male).
I can't actually find any new ebooks I want to read via Amazon recommendations any more. And this seems to be an outcome of deliberate changes? Why would they DO that?