Keith Ammann is the author of the popular D&D 5e blog “The Monsters Know What They’re Doing” which breaks down the stat blocks of all creatures in the monster manual and how you might best use them in combat encounters.
The blog’s popularity led to Keith writing a series of books on the subject, including "MOAR! Monsters Know What They're Doing", ”Live to Tell the Tale” for player tactics, and most recently “How to Defend Your Lair”, talking about dungeon, stronghold, and other structures and their purposes and layouts to make your players think strategically.