These books makes me want to run a GURPS game set in that era (early 5C BCE). Although I would recommend getting the Authors Bibliography, GURPS Low Tech, Greece, etc to run such a game. It would be a terribly small audience for such game sadly.
Its a great series, and similar to the The Saxon Stories by Bernard Cornwell. I was not much of a fan of the era, but these series made me a fan. I've always been curious about the Ancient Eras after finishing the lectures on Origin of Civilization, Ancient Empires before Alexander, and my own Chinese History studies that deal in the eras of the Shang and Zhou Dynasty.
I love how the author gets into the detail about training, conditioning, and discipline. It reinforces my own training and my own aspirations. When he does so it brings up is the amount of work it takes to be as good as the characters. Stuff I wish was an element in a game that people would enjoy like I do: enjoy choosing the best habits, routines, and training habits of my PC and managing his psyche. If I could afford a 40lb kit (which I cant) the stories in the book reinvigorate me enough to pursue crossfit weighted vest training as well as getting back into kali.
I love it when characters love training and making themselves better. They dont kill stuff to make themselves better, they train and the world turns. I like stories like that and which biases me to this book.
What I love about historical fiction is how it uses techniques in Non-fiction writing to amp up the emotional score of an event and action. It gives a lot of perspective and comparisons. Its fiction but the writer has some limitations with the material he has to draw from. Working with those limitations show techniques I can take up for my own storytelling.
The books are great and I bought them in Google Play store, because Amazon won't let me convert them to epub so I can use my Text To Speech app (@Voice Read Aloud) to listen to them as I have 2 hour commutes. The books are so well written It can convey its emotions even through the App.
Check out the Hippeis bibliography for setting research if you are going to try to get into it. Like in my basic understanding of Medieval Agriculture and Demographics it puts a TON of things in perspective and it enriches the immerision in the setting. The way the agricultural studies was important in the book, as the Author notes, Its my key challenge in my Chinese history studies.