Aaron is not Graham McNeil.
Outside the Black Library, Aaron has also worked on Hunter: The Vigil, wrote a short story for League of Legends From the Ashes and penned the short pieces of fiction, Dude, Where's my Land Speeder? and What it's like. He's well-liked by Daemonhunter lore masters, due to his effort in at least making the new Grey Knights lore more palatable (given the rage-inducing material he had to work with). Where there were once just Mary Sues after the Glory Days of 3rd Ed, now there is at least a semblance of deeper character to the 5th Ed Grey Knights outside the idiocy written by a certain Spiritual Liege. He even ties them back into threads left from Ravenor, so that the influence of Saint Abnett can cleanse them. In fact, he's pretty good at making all factions awesome but imperfect. See, for example, his portrayal of Angron: while Angron is indeed a dreaded unstoppable killing machine, he's also a pitiful character who blames others for his problems. ABD also wrote the greatest speech in the entirety of GW published works for Angron in Betrayer making him at once a figure of pity, a sad portrayal of a man whose lost his will to continue and a righteous badass on the search for revenge.
He has also committed himself to rehabilitating the reputation of Abaddon the Despoiler, with all the controversy that implies. He's certainly not above ripping into old Failbaddon either, as evidenced in the Night Lords trilogy where Talos has nothing but open contempt for him, point blank outlining all the reasons the Despoiler and his Legion suck, to his face. This is particularly noteworthy when contrasted with Talos' genuine respect for Huron Blackheart's power, authority, and achievements, even while planning on backstabbing the Corsairs.
He also wrote arguably the best speech in the 40k setting in Grimaldus’ to the people of Helsreach. It’s on his page, go check it out. Seriously, it’ll give you goosebumps.
Lest you think we're going soft, though, we should point out that he has received some pretty harsh criticism, particularly for his portrayal of the Emperor as a raging torrent of incompetence and jackassery the likes of which Earth had not seen since Mussolini made his last public appearance upside down at a petrol station (although, to be fair, some of these portrayals are from the point of view of traitor legions, who have a... less than positive view of the guy). Some have even accused him of turning the Horus Heresy books into a public therapy session for his daddy issues, which, to be fair, is comparable to CS Goto using his books as a public therapy session for his depression at not having the chops to be a Hollywood screenwriter. He also has a major issue with making the characters he likes look perfect while shitting on other groups; see especially his Grey Knights book which just becomes a Space Wolves wank, and The First Heretic, which is utterly fantastic - except the two pages his beloved Night Lords show up and snark all over the Word Bearers.
Insofar as one can actually speak for a large, completely anonymous community, /tg/ appears to have mostly turned against old Aaron. More and more he seems to be getting his way at Black Library, especially in the Horus Heresy series, and some well-loved fluff is being rewritten after a very long time unchanged. Many point at Master of Mankind, the book specifically about Big E, which no one at BL was smart enough to realize they shouldn't assign to the guy constantly criticized for how he writes that character.
Through his novels you can notice a handful of common themes:
- He likes Chaotic neutral(ish) characters.
- He is hence great at writing Robert E. Howard-styled characters (how is that he hasn't written any Conan pastiche?).
- He enjoys writing in first-point-of-view, although he can work in third-point-of-view.
- He mostly portrays Space Marines in his novels, although he has a few works with non-SM as well.
- If there is a ship at one of his stories, expect him to make the ship be controlled by a young woman. He says he tries to balance the testosterone with female mortal characters.
- He tends to write events through the protagonist's perception and thus has to spend lots of time telling people not to take the opinions of said protagonist (for example, anything said by or about the Emperor in MoM) at face value. To be fair, considering the average neckbeard's tendency to erect anything written as holy unalterable canon, it is a necessary reminder.
- He seems to have spearheaded breaking the classic image of the Emperor, turning him from a grimdark Sigmar into an emotionless Lex Luthor - this is still the approximation of "good" in 30k and 40k.
- He considers the 40k franchise fated to be won by Chaos. (It will be funny seeing him getting charged to write some stuff about Age of Sigmar.)
- He is quickly approaching Dan Abnett's record of number of beloved characters murdered. Seriously. Reading his books, especially the Horus Heresy ones, is like watching him rip your heart out and chew on it while he coos: "Was it good for you too?".