(If you're Graydon, sorry about that "abruptly". Seems that way to the rest of us, mostly.)
This is a strange book, and not just because it is cliche-looking military fantasy that veers without warning into the murky waters of "What kind of society are we fighting for?" and "What does an emergency backup plan for a civilization look like?" And then wanders back to the grueling magical warfare.
The writing style is that very particular brand of prose beloved of software geeks who learned people as a second language. It is careful, structural, recursive, and you sometimes need to read a line three times to see where it came from. I write this way. I try to go back and stick in periods and knock everything down to no more than three layers deep. I am being less careful in this review, because I've just read all of The March North in a sitting (long train ride) and it's sunk in some.
I don't usually quote in these reviews but I think I need to give the flavor:
"Passing for a Creek just to look at is tough, and if you look like a Creek, being anywhere near here without being able to explain where the previous six generations of your ancestors lived and what they did is impossible."
Got that? Good. And you will need to read those lines three times, because the author tells you everything exactly once. Maybe twice, for foreshadowing and resolution, but then one of them will be indirect. Blink and you'll miss major plot elements.
Blink and you'll miss the fact that the prose is entirely free of gendered pronouns. I noticed halfway through the last chapter -- I suspect the author deliberately stopped making it unnoticeable, there at the end. It's not a gender-free story; the narrator occasionally describes someone as a man or a woman; it just doesn't come up that often because this is the army and they're soldiers first. Without the pronouns, if it doesn't come up, it's not in the book. Take a lesson.
I haven't said what the book is about. Consider a world where magical talent has been popping up in the population for hundreds of thousands of years -- with a power law. So in a nation of (referring to the book) seven and a half million people, you might have two thousand sorcerers powerful enough to be effectively immortal and therefore become more powerful sorcerers. Fifty-odd who are powerful enough to subjugate the nation. A dozen who could wrap the nation around their pinky fingers and move on to the rest of the planet without breathing hard.
Dozens of better-known fantasy series match this template, if you strip off the fake-Euro-medieval assumptions and look at the guts. Few of them go on to the obvious question, which is why do you have a nation still standing? You should have a flaming wreck of a slave-holding ruled by one sorcerer-king and whatever demons, monsters, and slightly-lesser sorcerers he's bothered to brain-ream rather than kill. Or she. Doesn't matter to the slaves.
This book pulls an answer out of one additional assumption: that it's more efficient to pool power voluntarily than to coerce it. (Philosophically palatable to you and me, I hope.) Thus, the Line: a volunteer army that marches under a standard sworn to the Law and serving the Peace. With staff thaumaturges.
(Why does the Peace need an army? Because they're surrounded by militant sorcerer-autocracies, and also demons and monsters galore. Magic has not left a lot of friendly terrain on the planet.)
The slant of the military lifestyle is convincing (at least to me); the protagonist knows what both sergeants and COs care about. The protagonist also knows what an ox cares about, which is relevant both to the military (no army without supply wagons!) and the greater picture (armies fight, but someone's gotta grow the food).
The author is up-front about drawing inspiration from Glen Cook's Black Company stories. I'd also trace lines to Steven Brust (see the enchantress older than recorded history), John M. Ford ("he had a horror of being obvious"), and Derek Lowe's "Things I Won't Work With" chemistry blog.
There is also a five-ton war-sheep named Eustace. If I haven't sold you by now, I don't know what the hell you think you're looking for in speculative fiction.
(The March North is self-published as an e-book. If you buy it from Google Play you can download a DRM-free EPUB file. I think it's in the Kobo store too.)