Should this tag include stuff about print versions of HPMOR or Rationality: From AI to Zombies, or just the review collections from 2018 forward?
In my opinion, Rationality A-Z clearly yes. I mean, it is a book (an edited collection of articles), and it is related to LW.
HPMoR, yes, because it is important and was discussed a lot on LW. To be precise, the discussions are a reason to include HPMoR, but the discussions themselves should not be tagged (that would flood the tag and make it less useful), only articles related to making a book version of it.
I am less sure about Eliezer's other fiction (leaning towards no), or Unsong (leaning towards yes), or Inadequate Equilibria (undecided).
If there turn out to be too many articles with this tag, the tag description should contain canonical links to the individual books.