Well, to me there's likely no comprehensive theory of war today anymore. It's grown too large for our brains.
I consider the art of warfare instead as a huge mosaic picture; great theoreticians can add some mosaic stones and arrange many in a better grouping to improve the overall perception. A good book is one that adds a couple of mosaic stones to my perception of the art of warfare.
I'm really looking for advances and I don't see many in the open domain.

Poole is obsessed with "Eastern" style and seems to stretch anecdotes and military history to prove his point. His latest obsession seems to be with ninjutsu. He was still useful to tell about infantry combat concepts that don't depend on much material, though. He didn't seem to add much, instead he just illuminated some almost ignored parts of the art. I wouldn't call him "leading", but I would agree that he has succeeded in publishing and attracting attention.

I think that much of the theory generation has succumbed to the need to develop COIN tactics, techniques, and procedures that can be employed by infantry.
That's most likely true for the U.S. and to a limited degree also for UK, Canada and Australia. But we should have lots of theoreticians outside of the English-speaking world. Like France, Russia, India, China, Japan, South Korea, Germany, Italy, Spain, probably also Brasilia, Ukraine & Poland.
Germany has abandoned the open domain discussion of tactics after 1939, and what I can still see today are very tech-intensive attempts to partially approach the U.S. model. Our infantry is busy with peacekeeping anyway.