Published in 2014, Traitor's Blade is the first in the Greatcoats quartet of swashbuckler fantasy genre novels by Canadian author Sebastien de Castell. The narrative follows Falcio val Mond, erstwhile leader of the Greatcoats, an order of traveling magistrates who fulfill the king's law by dueling against local leaders who break it, and by singing catchy songs explaining the laws, so that citizens can easily remember them. Falcio is accompanied by his two oldest friends: Kest Murrowson, the greatest swordsman of his age, and Brasti Goodbow, a master archer with a wicked sense of humour and a profound detestation for knights.

The story begins in medias res, with the three Greatcoats on a bodyguard mission to protect a trade caravan's head merchant. At some time prior to the events of the story, King Paelis, founder of the Greatcoats and personal friend to Falcio, was assassinated by a cohort of dukes who opposed his laws; the Greatcoats, loyal to the king and his laws, were designated as personae non gratae, setting the rest of the country against them. Knights hate them as competition; the common people resent the Greatcoats for getting their hopes up about a better future, and then ultimately failing to save their king and permanently establish just laws. The prevailing central conflict of the entire series, in fact, is how severely the Greatcoats are hated by the very people they are striving to serve and help.

The novel is characterised by a tone of dry, wry, nearly self-deprecating humour from the first-person narration, and the author's experience as a fencer and fight choreographer is well utilised during the novel's numerous combat scenes. Similarities to Alexandre Dumas' The Three Musketeers are obvious throughout the novel, but they enhance the quality of the story rather than causing it to feel derivative, largely due to how often the author subverts reader expectations for swashbucklers. The narration alternates chapters between current events in the story, and flashbacks into Falcio's personal history. Combining this with the fact that he loses track of what he is doing at multiple violent moments in the story, and the reader is left to reasonably conclude that Falcio has severe PTSD: the flashback scenes are not merely Falcio relating past events to the reader; they are instances of Falcio actively flashing back to past trauma that his present circumstance is recalling to his attention, in the middle of combat or other stress. Traitor's Blade is entirely hilarious at times, owing to the silver tongued protagonist's talent at talking himself into and out of trouble, but it also features multiple extremely dark (and fairly explicit) moments which render it unsuitable for younger readers.

Traitor's Blade was a finalist for multiple awards following its release, including the 2015 Gemmell Morningstar Best Debut in the United Kingdom, the 2016 Prix Imaginale for Best Foreign Work in France, and the 2016 John W. Campbell Award for Best New Writer in the United States.

The author keeps an active blog where subscribers can gain preview access for free to short stories attached to the Greatcoats series and others. The next book in this series is Knight's Shadow, followed by Saint's Blood and then Tyrant's Throne.

Iron Noder 2018, 19/30