Not Graeme Lyon.
In all seriousness, Chris Wraight is a newer Black Library writer, and so far he doesn't disappoint.
His works so far consist of:
Wrath of Iron, another Space Marine Battles novel, where the Iron Hands fight the forces of Slaanesh while being extremely awesome, though also being massive dicks in the process. Nice to see the Iron Hands getting some time in the spotlight.
Iron Company, a WHFB novel I haven't read. Also Sword of Justice and Sword of Vengeance, both are pretty damn good WHFB books focused on Ludwig Schwarthelm and Kurt Helborg, both are pretty damn badass.
Kraken, a Space Wolves short story about a bunch of humans on an water world getting their ship-cities wrecked by mysterious sea monsters who call on space Marines for help, but get a lone wolf instead. Some minor but noteable lulz when the people can't quite understand how the fuzzy faced giant covered in pelts could be a space Marine.
Brotherhood of the Storm, a recent limited edition Horus Heresy novella about the White Scars and the event that caused Horus to mistakenly assume the Khan would join him.
Scars, a full length Horus Heresy novel following the Khan as he decides whether to side with Horus or the Emperor.
Path of Heaven, a sequel to Scars that gets right into the fatalism and misery of the late Heresy, as well as the shenanigans involved in the Webway project. Manly tears occur.
Blackshield, a short story about an ex-Deathshroud renegade. Along with Demonology and the Death Guard appearances in the WS novels, he's probably going to write the downfall of Mortarion.
Leman Russ: The Great Wolf, a Heresy-era novel about, you guessed it, Russ.
Carrion Throne and the Emperor's Legion, the first 40K books to really get involved with the Custodian guard.
He has a Space Wolves short story and two full Space Wolves novels out and they're all pretty good. Blood of Asaheim and the following Stormcaller novels are both standout grimdark that bridge the gap between William King's happy-go-fluffy wolves and the thinly stretched, stubborn bunch of rip and tear fucks we know them to be.
He's also written 'Jaghatai Khan: Warhawk of Chogoris' for the Primarchs series of HH novels. This should deal with the founding of the Librarius.
He wrote Watchers Of The Throne a really good book dealing with the Custodes, Sisters and the high lords in 40k. Manages to flesh out all 3. Moved the Custodes away a little from being the heartless bastards from MOM and even manages to make the high lords sound at least competent. The Sisters especially Aleya are also very cool.
Unfortunately, he had quite a big problem with plot consistency and following the fluff. For example, in his Thousand Sons novel Bjorn was described as having an assault cannon, and a few pages later he shoots plasma bolts at a heavy robot (and oneshot it, which is also bullshit, considering Cataphracts are fuckhuge heavily armored killbots, which are extremely hard to bring down even with proper anti-tank weapon). Add to this a Blood Claw Dreadnought, Grey Hunters charging at Thousands Sons through inferno bolt fire, sustaining no casualties from it, and than being unceremoniously wiped in melee by said Thousand Sons, Magnus forgetting he's a god damned unstoppable magical killing machine, capable of nuking titans and entire cities and rushing into close combat where he got his ass handed to him by a Dreadnought, and you would got the picture. To be fair, the Battle of the Fang couldn't be lost by the Space Wolves, so Chris was all but forced to write stupid things to fit the stupid old fluff written by his predecessors. It could also be the sign of a newer author simply making mistakes or been overly enthusiastic about the lore as things like this have lessened considerably. He's definitely improved in this regard since, with both sides in Path of Heaven displaying reasonable tactical nuance.
-The above criticism is fair to a point, the Grey Hunters were slowed by the sorcery of a Thousand Sons sorcerer and were outnumbered 18-11 so it's not totally unceremoniously wiped. The Blood Claw dreadnought is an odd addition lore wise but the character is pretty neat, especially as it gives an insight into how dreadnought pilots feel and the interactions between him and the mortal Freija is insightful at times into the customs of Fenris. Bjorn only has his claw descibed before the battle with the robot and even then when his weapon is mentioned, it's a plasma cannon, only the cover art shows an assault cannon so that isn't the author's fault. (pg 385)
His biggest strength so far seems to be fleshing out Legions and other factions who've had very little love previously. A lot of people who never liked the Scars have been won over by his portrayal, and he's even done a good job on the Emperor's Children and Death Guard as antagonists, midway through and still putting off Chaotic corruption, respectively. Fuck, he's made Eidolon competent whilst not just turning him into a totally new character. Also wrote the first proper description of Terra itself in Carrion Throne, and it is AWESOME. Someone add shit to this page it's a fucking disservice to the guy to have this little and i'm too fucking lazy.