The Monsters Are Smarter Than You

There is a blog written by Keith Ammann, author of The Monsters Know What They're Doing, MOAR! Monsters Know What They're Doing, and Live to Tell the Tale that can be found at this address: www.themonstersknow.com  <----- Link

I have the first two books by Keith and recommend them to any DM. The information within is written based on 5th edition D&D, but the ideas can easily be applied to any edition when thinking about how to use adversaries in combat. 

The Monsters Know What They're Doing is focused on creatures and NPCs from the 5e Monster Manual. MOAR! Monsters Know What They're Doing deals more with creatures and NPCs from supplements like Volo's Guide to Monsters and Mordenkainen's Tome of Foes.

I do not yet own a copy of Live to Tell the Tail. That book is geared toward helping the players handle their characters more efficiently in combat and I expect it could prove useful when playing with a DM informed by the previous two tomes.

The books are not printed on fancy paper or heavily illustrated. They are thick works with large type (thank you Keith from all of us grognards with declining vision) and sturdy hard covers. The information within both Monsters books sticks mostly to conveying the thought provoking tactics and techniques a creature likely will apply in a fight against adventurers.

Monsters and NPCs should not cleave to the ideas offered slavishly, but should instead modify their tactics based on terrain and the situation. It can't hurt your story if foes are not at their optimal state for every circumstance, sometimes the environment and/or the timing is terrible for them. However, having the player characters face foes in their element will turn what players might expect to be a cake-walk into a memorable battle and might even force an occasional retreat!

Without a doubt these guides will give a DM the tools to make combat more interesting and exciting, and most of us would agree, that is a good thing.