Sacrosanct
Legend
My favorite supplement of all time was AC9, Creature Catalogue, and my second-favorite was AC10, Bestiary of Giants and Dragons. Neither of them made the list for some reason (grumble grumble), so I was upvoting the only BECM supplement that did (Shady Dragon Inn, somehow). Now it's gone, so there's really nothing left for me to upvote on purpose. Guess I'll roll a d4...
Books that are primarily only monster manuals are exempt. Volo's guide has a lot of info beyond just a monster manual, despite the name.
And I'm downvoting VGtM for its price tag alone.
Volo's Guide to Monsters (5e)--19-2=17 Fifty bucks? Seriously?
The Complete Guide series were $15 25 years ago, and they are pretty basic and thin books with a much lower production value. So $50 isn't a high price in today's dollars at all.