I get notifications from Amazon about particular author books by "following" the author.

For example, here's Fran's author page. Click the "follow" button under her name and you'll be notified when her next book is released. [link]

I’ve tried that before and it only sometimes worked, weirdly. Or it would only tell me after something was out already, etc. plus there are some authors where I like one series but not others of theirs…

Meanwhile Amazon frequently sends me emails about books I “might like”, that bear no resemblance to anything I’ve ever bought for myself or others.

I seem to get a lot of these type of messages from Goodreads. But if you're not already on it, it'd be a pretty labor-heavy way to get set up with books you've marked "read" and/or authors you follow to get notified of new stuff.

I get a list of books under “continue series you’ve already started” on my kindle, but it’s not comprehensive. I think it did recommend Demon’s Daughter but only after it had been out for a while, when I get month’s of reminders to pre-order books that I’m far less sure I will want (I’m trying to wean myself off of at least some of the series that I just don’t like that much but keep reading out of inertia. It’s a challenging goal). Like many Amazon recommendations , what it mostly does is recommend the thing I just bought. It’s possible that my tendency to binge read everything I can find by an author has messed up the algorithm, but knowing that the automated processes they use to order from vendors is similarly wonky (or appears to be) I suspect it’s an intrinsic issue

Hah yes I get the “you might like” on my kindle but it’s a bit swayed by my tendency to read a lot of trashy romances on kindle unlimited.

In the case of Bujold's Desdemona e-books, they're self-published and I get the impression that she only sends the files to Amazon and other sites when she is satisfied with them. Whereas with books put out by standard publishers get announcements in various forthcoming book places (Locus, etc). Amazon probably gets announcements about them early on just like those places.

Fair! And a few of the other authors I like are self-pubbed as well,and I’d believe that.

I just finished The Mimicking of Known Successes and immediately preordered the sequel. Very good and thinky, in the ways I like my sf to be, with interesting characters and plot to boot.

Nice. I've had a sample of that sitting in my TBR for months but I keep getting distracted and reading something else. Maybe it will actually float to the top, now!