This book is awesome, even when there is no great military campaign involved. Humanoids are great foes as they should use tactics when engaging, and this booklet actually encourages it, giving several hints of how to use them to fully exploit their uniqueness. But what I like the most in this book is the little hints of worldbuilding underlying on the descriptions of several units, as the dragonborn mercenary companies or the halfling slingers. A great add-on to any campaign.

An excellent source for NPCs that would appear in an army. I have not had time to run any numbers, but the stats seem well balanced and the author does a great job of giving a brief setup for each entry. If you are worried about the Author's statement that English is not the Author's native language, don't be. While there are small usage or word issues, the work is still very clear. I wish I could trust myself to be as clear in another language.
As the Author notes, these are Stats for the groups of soldiers and attached personal found in an army. The Armies covered are the standard Human, Elf, Dwarf types expected in such a product. Where this product really shines is in the other armies covered, such as an Undead Army, an Infernal army of Tieflings and a Fey army. In many ways the feel is like a Warhammer army list, but set to use in 5e encounters rather than minature warfare. This would be a great product to use to create a section of an army for your Characters to interact with when they find themselves caught in a war zone.
Overall, a great addition to the NPCs in the Monster Manual and a product I will keep up with as the author updates it further. The only negative, I would give it is the same one most products have on this site and therefore not something I'd drop the rating for. The use of a color background is painful in printing even it looks nice on screen. A printer friendly white background would certainly make this old gamer, who prints everything to read, a happy gamer.