Each post breaks down a particular monster or monster type, looks at their writeup and stats, and assumes that, you know, the monsters aren’t dumb. They’re optimized for filling their ecological, magical, or theological niche and don’t suck at it.
What does that mean? It means that your encounters will get a hell of a lot more interesting and flavorful. A pouncing predator will hide. It will wait for the right moment. It will strike and try and kill its food and drag it away pretty instantly. It will not stand and fight in a pitched battle, and if threatened or injured before it has a kill, it may flee. It may well return.
But by looking closely at how each monster type should behave and best utilize it’s listed stats, and also how the “fluff” and description of the critter places it within its niche, he comes up with concrete, actionable behaviors that will make each fight or potential fight (because maybe you can frighten off a predator with a threat display) feel different than others.
Each monster writeup in The Book of Foes contains a short nugget on how the critter fights. Keith’s blog takes that to 11 each writeup with the kind of detail and care that sings the song of a man who loves his topic.
He’s also just released a book to ensure that the PCs should know what they’re doing too: Live to Tell the Tale. Since I love supporting this sort of thing for reasons including healthy dollops of both altruism and self-interest, I highly recommend checking out his stuff. Even if you don’t play 5e, how he thinks about tactics and abilities is transferable to any game.