The Rhenwars Saga can basically be summarized as a five book saga (technically 4 books + 1 prequel) which chronicles a world which is divided into half by a group of heroes who tried then failed to save the world 1000 years earlier. To explain the plot of this will spoil previous books, so be warned. *SPOILER* The protagonist, Darien Lauchlin, gained Rand al'Thor-esque powers of near-godlike power after the massacre of his order of wizards only to employ them in a forbidden fashion to kill tens of thousands of Darklanders.
He then trades his soul to save his deceased girlfriend, only to find himself a servant of the god he's opposed all of his life and given the task of saving the Darklanders. Much to his surprise, he finds the people on the other side not really different from the ones he fought for and this makes him history's greatest mass murderer rather than a hero--especially when his own people want to exterminate the one he's now protecting.
M.L. Spencer is an interesting variant of grimdark as the actual story doesn't contain any of the usual qualities of the genre like explicit sex, foul language, or even gratuitous violence. Instead, the darkness of the story is born from the razor's edge between good and evil that consumes almost every character. Character after character goes from being a hero to a villain, particularly in this volume, with them dying screaming for the blood of the enemy.
I'm no stranger to writing deconstructions of traditional fantasy stories but M.L. Spencer one ups me by making a tale which really highlights a world where the typical tale of empires, kings, and warriors becomes a gray and gray war with no victors--only survivors. One man's demon is another man's angel, it seems, and we get to see what could be a set up for all of this war proving to be pointless. After all, in the prequel, none of our hereos' efforts mattered because the world ended up destroyed by a cyclical natural disaster they couldn't prevent.
A cycle which is set to repeat soon.
Is there any flaws to this work? A few. I think Darien has way-way too much luck with the ladies, with seemingly every female character in the series wanting to bang him. There's Meiran the Archwizard, Naida the Priestess, Arda, and even a female who offers to be his concubine. This is all in this single book as well. There's also a bit of a disappointment with some of these characters' fates as some of them I felt still had good stories left.
In conclusion, everyone who got the previous books should continue reading as the story has set up for an exciting climax. There's lots of moral conundrums, corruption, and tragedy in one of the best fantasy stories I've read this decade.