Shared-universe fiction asks something unusual of a writer: to work inside a setting built by many hands and still sound like nobody else. Chris Wraight does that in the Warhammer 40,000 setting, where Ashes of the Imperium takes its place in the vast Horus Heresy sequence.
The mode is military science fiction with the volume turned up, though our catalogue also tags it as fantasy, and that is not simply an error. This is a universe where the machinery of science fiction runs on something closer to myth, and the writing takes both halves seriously.
The pleasure of the sub-genre at its best is interiority. The battles are there, at scale, but so is the question of what enormous events do to the people caught inside them, and that is what lifts tie-in fiction into something worth returning to.