Not looking for a 600+ page tome, a book in the 200-300 page range or a lecture series would be optimal.
The author Kirk McKusick has some excellent videos on YT too. May not cover all you want as he used to sell a video course on his home page (his site isn't loading for me, so I can't check). Should give you a start though. Trivia: The magic number of the UFS2 filesystem is his birthday as Easter egg :)
The first edition is freely available on FreeBSD's site https://www.freebsd.org/doc/en_US.ISO8859-1/books/design-44b... Note that this is based around 4.4 BSD so some recent features will be missing.
Bach's Design of the Unix Operating system is horribly outdated these days.
I'm not aware of anything shorter that I'd recommend.
An operating system covers quite a lot these days so a short book would either skip a lot of topics or be very shallow in the specifics and the specifics is very much at the core of coding an OS. You need to know a lot of the environment it runs in, so it becomes detailed rather quickly.
I'm ok with that! I'm not planning to write an OS, just want to have a programmer's mental model of how an OS works.