A Black Library writer. He's not C.S. Goto or Gav Thorpe, but he's got a big problem: he has zero understanding of why fans of a given faction like that faction. The worst offense is his treatment of the Iron Warriors, who he writes as complete retards who only win because they're lucky and have no self-control. Us Iron Warriors players like them because they're the most disciplined and pragmatic legion; the one that will do anything to win. John French doesn't realize that good characters have goals of their own. The Iron Warriors want to build their own empires after they're finished wrecking the Emprah's. But nobody told Johnny.
His Ahzek Ahriman book series is pretty good though, it's worth a read. Furthermore, he does a great job with the Imperial Fists, as The Crimson Fist and especially Praetorian of Dorn show. He completely nails their sense of duty and their stoicism, as well as their deep-seated fear that they aren't good enough. The Alpha Legion's contingencies and adaptability are also written believably instead of overdoing their mysteriousness. Ultimately, he portrays the bleak, "black and gray" morality that defines 40k while exploring elements of 40k frequently glossed over. 9/10 times, he writes an interesting story that focuses on right and wrong over smashing skulls, with very thought-provoking twists at times.
To summarize, HE CANNOT BE ALLOWED TO WRITE IRON WARRIORS
In this he's kind of similar to ADB. Both are excellent writers but completely ruin certain factions. In John's case its the Iron Warriors in ADB's case its the Emperor.
While Iron Warrior Fans hate French, it's because he has a different opinion of them and Peturabo that fits another side to them. French paints them as a grim force that cares nothing for casualties, to the point where their Primarch would kill a tenth of his Legion just to teach it a lesson. Hos Peturabo is the Iron Tyrant, Space Stalin, all the bloodstained dictators of history but as a Primarch. Some non-IW fans argue that this interperetation is equally valid, or even Perturabo's "true" personality, but there's a clear line between being brutal and mercilless in order to win and idiotically throwing away resources. In Extermination, French writes that Perturabo decimated his Legion to make them willing to accept any number of casualties in order to win, after the Legion had just crippled itself as a military force because it was willing to accept any casualites. You read that right. He literally wasted a tenth of his available manpower to get the Iron Warriors to do the exact damn thing they were already doing. Every writer paints them as not giving a shit about casualties, but French writes them as pointlessly wasting lives where other writers who have a better grasp of the Iron Warriors show them being grimdark and evil, but calculating and efficient rather than uncontrolled morons. French just decided he likes the idea of the Iron Warriors caring more about revenge than themselves, and fuck anyone who got into the Iron Warriors because they're the Chaos Marines that have their own ambitions and character.
With the sad death of Alan Bligh, John French has taken over as the main fluff writer for Forgeworld's Horus Heresy Books. Expect butthurt Iron Warrior Fanboys when French writes the Battle of Tallarn book.