So speaking of Dune, I preferred the Dune Encyclopedia, which among other things included recipes for Fremen Bread.
I can see it now . . . an advertisement for some yet-to-be-written sci-fi epic:
" . . . order the stunning and critically acclaimed
Starstung Trilogy today at your favorite bookstore! (Authorized Starstung Dictionary sold separately.)"
MUWAHAHAHA-HA-HA!
Really, I don't like the trend. Time was, that works of fiction almost
never needed glossaries or dictionaries, because the book or story itself gave you everything you needed, within its context. Some of them needed a map, thoughtfully provided inside the cover at no additional charge. I think it's unkind and thoughtless -- and maybe even a symptom of laziness -- for a writer to force the reader to look up references in order to know who's who and what's going on.
Remember, "Easy reading is hard writing."