Not sure what to think about the guy honestly.
The Heresy Series really gave McNeill a chance to develop himself as a writer. And for a while it did. He had an excellent opportunity with A Thousand Sons to really study his characters and add their flaws. The debates we have had on these forums about whether Magnus was a piece of shit or a loyal son have been such great debates. And its because of the fact that McNeill was able to show both sides well and let the reader chose what to think.
McNeill's most masterful line was when he makes Magnus say something along the lines of, "They were going to destroy the library... and I stopped them." So many readers pretty much leave this book thinking the Thousand Sons and Magnus were picked on and didn't start anything. McNeill allowed reader to absorb everything else and avoid the little hints. It made the story beautiful.
The reason I mention A Thousand Sons is because it just seems so strange how bad he displays the villains in most of his novels. With Angel Exterminates, I feel he tried to display this, by making Perturabo look like a bro and his legion a bunch of crazy incompetent idiots. If an Imperial Guard regiment was depicted like that I wouldn't have taken the novel seriously.
Its that stereotypical villain that Mr. McNeill has fallen back on like a bad habit. Its absolutely disgusting, when considering how authors including himself have worked really hard on their novels to display the fallen legions with different aspects of evil and good. Its what I've said countless times, which is the fall of the legions was a folly well beyond simply the Imperium losing half of itself, but an Imperium fighting half of itself. How many times before the heresy and even a bit after have we heard, a war where brother fought brother and killed because of different beliefs. The emotion and true drama in the series is that the legions had fought side by side like brothers to make something beautiful and then tore each other apart.
Instead we have authors that do this stereotypical villainous horse shit. Evil laughter, curling their mustache and plotting to defeat the true good which is the Imperium. Its fucking dog shit.
Unfortunately, McNeill really puts himself in the middle between success and shit that has seriously damaged the series.