There are too many 5-star reviews IMO, so I'm gonna be specific.
Told in 3rd person, this is a grisly fantasy series with utterly disgusting villains and too many battles / not enough strategy, but I liked some of the characters enough to stay with it. Deathclaw is a favorite especially, and the rogue horse Gwyrtha (sp?). The ogre Fist is also a winner, but squirrel? Really? Are we children? As to that, there is no sex and no cussing, so the book could appeal to older kids, if they can handle the torture, mutilation, mutation, etc. There is a little romance, too.
Writing quality of entire series:
The writing quality is okay but yet somewhat troublesome. I hear the author's modern language too often (example: "he's a major player"). Cooley writes "pretty much" or "not that much" or "not that bad" etc. Unlike Tolkien's Middle Earth, this language just didn't feel like a medieval world.
Some plot holes. Example: When Ewzad Vriil died all his mutated monsters died. So why didn't Talon and Deathclaw die, too? Why did the modified trolls survive?
Characterization is sometimes inconsistent. Breaches occur. Example: The good Prophet makes the weary and injured protagonists trudge up numerous stairs immediately after an exhausting battle, still bloody, thirsty, and hungry, just so he can tell them a long story -- and right now, bloodstains notwithstanding! This behavior contradicted his wise and kindly portrayal and made me question his character.
Another example: The author sets out to convince the reader that a character is battle-wise and experienced, but then has that same character do something so glaringly stupid (not immediately ensure a beast is dead) just to steer the plot and create tension. Another character is portrayed as tremendously caring, but then he recklessly puts everyone at risk in battle just for his own egotistical reasons. A person doesn't wear armor in battle, for no reason but to allow him to be badly wounded (everyone else wears armor). A person has a magic bow with unerring arrows, but he repeatedly decides not to use it for some trumped up reason (just to create more tension).
The hero Justan is supposedly a brilliant battle planner, but we see little evidence of it. In terms of tactics and strategy, Justan compares unfavorably to Miles in Bujold's Vorkosigan series, Tavi in Butcher's Codex Alera, Hal in Flannagan's Brotherband series, or Will in his Ranger's Apprentice series). Compared to all these strategists, Justan's ideas tend to be fairly basic, and are presented almost as afterthoughts.
But the dwarf Lennui is consistent. He's consistently annoying, inserting "dag-gum, dag-blamed" etc into his dialogue. Nearly every sentence.
Pseudo-secrets are contrived and disguised as real suspense. Too often, the author creates a dialogue where someone asks a valid question and for whatever reason, his friend won't answer. "Not now. It is too soon for you to know about this. I will tell you later." Or "This must remain a mystery. The Creator won't let me tell you." This happened a lot with Coal, for example, but also with the good Prophet, and with his mother, etc.
The author misuses words in this series (infer should be imply, reign should be rein, and subjectify isn't a word). In addition, I encountered a handful of basic spelling and punctuation typos.
The writing flaws bothered me, but the likable characters kept me going. And I did like seeing some characters change in credible ways over the course of the books.
And thus endeth the first five books, with a spin-off continuation series to immediately follow, so the story of the Dark Prophet doesn't really end here. In fact, the spin-off series "Jharro Grove" appears to be largely a reincarnation of these first five books, according to the plot summaries and reviews.