I enjoyed The Face of the Enemy enough to buy this sequel and I am glad that I did. From a literary perspective, it is an improvement on almost every level. The character development is more rich, the plot tighter, and the battle scenes more compelling.
Picking up shortly after the first book, the focus of The Nature of the Beast is direct military confrontation with the Remor. Humanity is launching its first real counteroffensive, but its commander and his troops are not exactly the cream of the crop of the Interstallar Defense League. At least on the surface. To make matters worse, the IDL force has to deal with a large contingent of civilian volunteers from a a star nation whose human government has refused to sign up with the IDL. They are eager, but naive, underequipped, and undertrained.
In addition to following the IDL's preparations, you learn about life on a Remor occupied planet. Which is kind of surprising because you got the impression from the first book that there would be no humans left after the Remor got done with them. But it seems that the Remor have their uses for humans which makes the Remor far more heinous than had they simply just exterminated them all.
Fawkes follows both narrative threads in a balanced manner, giving each sufficient attention so that when the narratives converge, the story moves along smoothly and naturally.
The battles in space and on the ground are more detailed and developed than in his first installment, though not as global as you will find in other science fiction. Though in the first book, the IDL characters sometimes seemed a little one dimensional, here they have more depth. More honor. And certainly more justification.
In the first book you learned more about humanity and its varied governments, motivations, and space nations. This book tells us a lot more about the Remor and, perhaps, their motivations. In my opinion, Fawkes has done a good job of "setting the board" for future books about this universe.