The quick take on the book is it's the French Revolution with wizards, but it expands beyond that reductive framework swiftly. A so-called "flintlock fantasy", it makes good use of the setting with the introduction of the (trilogy-titling) "powder mages", a comparatively new brand of magic user whose abilities are all tied to gunpowder. It helps that the powder mages' magic operates by a fairly clearly delineated set of rules from which possibilities ramify (a la Sanderson) rather than by the vaguer "and then the magic stuff happened" approach. This helps make the various nifty feats that characters get up to with them feel earned, rather than a product of authorial handwaving. That said, though they do get some light explication, the other major class of magic user (the so-called Privileged, who - you guessed it - are overwhelmingly on the side of the monarchy) are definitely on the vaguer side when it comes to the rules limiting the possibilities of their magic. 
 It also has complicated, intriguing, and often morally ambiguous characters. It's never entirely clear exactly where Tamas, the prime mover of the plot and central character, is going to fall when questions of justice vs. vengeance, expedience vs. morality, and so forth arise. This helps keep the tension going and the character interesting. I'd like to say more about the other characters, but to mention every character I found interesting would essentially require naming every major viewpoint character. McClellan does a good job here. 
 Without going into spoilers, there are three main branches of conflict for the protagonists to face. First, there's internal intrigue, some involving predictable backlash from royalists and the survivors of the nobility, some involving foreign enemies, and some involving shadowy figures whose motives have yet to be explicated. This makes for quite the bubbling brew indeed. 
 Second, there's a battlefield confrontation between the nation's numerically inferior but higher-quality troops against the mass of numbers of their hostile neighbor (also involved in aforementioned plotting). Honestly this felt probably the most familiar of the plot elements, but it was handled reasonably well and it's a trope I tend to enjoy personally, so I'm not too apprehensive that it looks like it'll be heavily foregrounded in the sequel. 
 Third, there's the stirring magical forces in the background. I can say the least about this without risking spoilers, but suffice to say the overthrow of the monarchy looks to have sparked a magical upheaval to dwarf the already considerable social and political upheaval occasioned by the same. Some of these also look to be involved with the aforementioned plotting as well, but there are enough shadows still present that it can't be said for sure. 
 On the whole, this was a well-crafted and exciting book. Honestly probably the worst thing I can think to say of it is it left my uncomfortably impatient for the sequel.