I was kind of disappointed in this book. I definitely really like parts of it, but overall it wasn't what I was expecting, and I don't think I'll find it super useful.
It's got a ton of good ideas, but they are buried under poor writing and filler, and some are underdeveloped. His writing style is very chatty in a way that turns me off; I keep skipping whole paragraphs thinking "Get to the point, already!" The game mechanics are often worded poorly -- like, I know what he means, I think, but maybe someone with a better grasp of 5e could have given this a once over? And honestly, I don't need footnotes about why the French invasion of Russia failed; save it for forum arguments.
Much of the book seems like padding just to increase word count or persuade the reader of something. As an example, on page 11, there's a half-column sidebar entitled "Paying More To Get It Done Faster," which has 3 paragraphs of text that can basically be summed up as "You can't." Not only is this answer wrong (he cites The Mythical Man-Month as proof, but that's a book about software engineering, which is a very different endeavor than construction), it's also boring. It would have been faster and more interesting to say something like, "Hiring more workers and better supervisors can speed things up, but with a sharp diminishing return. Reduce the time by 10% for every doubling of gold spent." That's such a steep cost that most players will not pursue this path. But instead, he writes 3 paragraphs about why it won't work.
Now, all that said, there is tremendous creativity in this book. I particularly love the monsters in the appendix -- these are fantastic, in multiple senses of the word. I love the freakish angels and the tentacular Court of All Flesh and the robotic Inexorables. Even the gem dragons are presented in a pretty cool and interesting way. I also love the "Strongholds by Class" starting on p.40. These are very evocative, and it's neat how they apply "Lair" effects to PCs. The Follower tables are a really good and concise combination of flavor and mechanics that work really well. And the fact that each class's info fits on a single page (except Paladins, who get more goodies) makes it very easy to digest (unlike the rest of the Strongholds chapter). The DM advice is also pretty good, and I appreciate all the times when he points out alternate approaches the DM could take, so that people understand which parts of the system can be flexible without becoming broken. Finally, nothing I've criticized so far applies to the excellent Warfare rules in the appendix -- those are tightly crafted, and the writing gets right down to business.
In short, it seems to me that Colville is really excellent at coming up with creative and useful ideas, but should really pair up with someone who knows how to write rules text, or maybe with a ruthless editor who is willing to take the red pen to all the extraneous filler. If I were actually going to use this book in game-play, I'd probably print out page 10 (stronghold cost & time) and all the class-specific pages, and then wing it from there.
