It is difficult to give a decent review of Last Argument of Kings, final volume of the First Law trilogy, without some spoilers. So I'm going to split the review into two parts, firstly about the general style and then about the story, with a warning when the spoilers are due. 
 On the whole, Abercrombie's writing is pretty good - vivid description, good character voicing and development, excellent plotting. Sometimes it reads as though it's short of a final edit; my personal bugbear was how much all the characters 'grimaced'. I was grimacing every time that word came up. I don't know if I just noticed these flaws more in the second and third books, or whether the first was more polished and then the others where slightly rushed. What he really excels at is tone. There's a plethora of darker fantasy out there, gritty realism introduced into fantastical settings - I reckon people influenced by reading Robert E. Howard - where the combat is bloody and dangerous, characters swear in the kind of situations when real people tend to (not made up curses of the "by the teeth of Karvik!" sort, either). A lot of that sort of fantasy, even the good stuff like KJ Parker and China Mieville, tends to be a bit on the humourless side. Abercrombie has a deft hand with tone, creating real tension and then relieving it with humour without descending into farce or any danger of becoming 'comic fantasy'. With several of the main characters we get a third person view (hearing?) of their inner monologues, which helps us get to know them through their foibles and self doubts but with which he also does a nice little trick. Each of these characters has little repetitive phrases that recur sporadically - Logen Ninefingers muttering "still alive" after every fight, Glokta asking himself "why do I do this?" or musing on the possibility of being found floating in the docks. This would be an easy tool to overuse, and become extremely annoying, but used sparingly it helps to cement the character voices as well as the plot structure, as leit motifs which both mirror past events and foreshadow future ones. The fight scenes are satisfyingly bloody, although I think he overdoes this somewhat. While not all the fights are described in detail, a few more could have been glossed over. Because Abercrombie has to keep finding different ways to describe the splatter of blood and the mutilation of body parts, it does become a little strained by the end and somewhat overshadows the feelings of the characters involved in the violence, which earlier on took precedence. Perhaps four stars is a little generous, but I think they are deserved for ambition and achievement. 
 Now, on to the review of the story and the inevitable spoilers. 
 Any genre of fiction has its themes and tropes, its styles and conventions, with which most of the readership are familiar. Terry Pratchett's early Discworld novels are a classic example of an author taking these conventions and twisting them for effects both comedic and social commentary. If you read Pratchett without knowing these tropes you're missing half the jokes. It's like reading the Dilbert cartoons without having worked in an office. 
 In heroic fantasy two of the big conventions are the mighty-thewed hero - often a Northern barbarian, usually smarter than he's given credit for, sometimes prone to berserk battle rages - and the centuries- or millennia-old wizard who watches over the world trying to steer civilisation and/or thwart the machinations of his dark adversary, often by use of pet heroes. In The First Law trilogy we have Logen Ninefingers, most feared warrior in the North, and Bayaz, First of the Magi. It is the riffs that Abercrombie plays with these conventions are what really makes these books worth reading. 
 Logen is a trouble magnet. We first meet him barely surviving a fight which leads to him falling from a cliff (the common trait of heroes in any genre is a huge amount of luck, both good and bad). We find that he is considered the most dangerous man in the North, but seeing him in a series of fights we wonder whether this is just luck. He is tough and capable, but seems no more so than his erstwhile companions, a group of other Northern 'named men', fighters who have made their names in battle. Until, at the end of the first book, we see Logen in his berserk rage, an unstoppable killing machine who recognises neither friend nor foe, just targets to be slain. And Abercrombie makes this interesting by introducing a touch of reality. Logen knows what he is. He has been fighting and killing for too many years and is sick of it. Not only does he know that he has killed companions in the blood heat of battle, he looks around and sees that everyone is either terrified of him or bears him hatred and blood feud, or both. But war is all he has known and, as someone remarks, the better you get at killing the less use you are for anything else. Logen makes the resolution to try and be a better man, but his only use is as a warrior, a killer. 
 Bayaz is a wizard more in the mould of David Eddings' Belgareth than of Gandalf. In appearance, a hale and hearty individual of late middle years, grey haired but solid and no nonsense, he doesn't mind becoming involved and getting his hands dirty. We only meet him going on for half way through the first volume, and at first his role seems more that of a facilitator than a protagonist, although the clues are there from the start that it is otherwise. Bayaz is more than a thousand years old, once favoured student of the creator of magic, and now first in the art. He was responsible for founding the Union, the kingdom which is central to much of the action and politics of the books. Bayaz is undoubtedly wise and powerful, and certainly appears benign in comparison to what we learn of his arch-nemesis, who controls the Gurkish Empire, a southern desert-based nation and main rival of the Union, by posing as the prophet of their god and controls a cadre of warrior magicians who gain their power by eating human flesh. 
 It is only in the second half of the final book that we learn just how involved Bayaz is, although the clues were there. From the start, he has orchestrated everything. While he takes credit for helping win the war which is the focus of The Last Argument of Kings, he deliberately planned it to draw out his enemy. And that is the point. The sorcerer is not concerned with the well being of people or the advancement of civilisation, but in proving himself the most powerful magician of all time and demonstrating that power to his nemesis and exercising it for his own ends. When Luthar, a shallow, self-centred military officer who Bayaz has manipulated onto the throne of the Union tells the wizard how much he hates him, Bayaz laughs. "I couldn't care less what you think. You people live so briefly and die so quickly it isn't worth bothering with. You are insects." 
 Throughout the trilogy there is movement toward redemption. Logen trying to leave a life of violence behind him. Luthar realising he has lived a life of privilege and selfishness and changing his ways. Glokta, once a dashing cavalry officer who was broken in the torture chambers of the Gurkish Empire and is now chief torturer for the Inquisition, constantly questions both the morality and the point of what he does. Although in the end there is no redemption, which is a necessarily bleak outcome, it feels as though this is only due to the imposition from above, that things would have worked out better were it not for the malevolent, all powerful force that has its own agenda and to whom humans and indeed nations are simply pawns.