Spectacular novel. Coming off of finishing Deliverance Lost and the differences were very palpable. ADB is just a superior writer, both in technical capability in pacing, and in overall structure. And DL was OK...I just never invested emotionally with any character, scene, or situation.
His vision of the GK stands in quiet contrast to the Codex, which was overblown pomp and fanwankiness. The GK never worked as an army to me anyway. Were I playing many games of 40K, I'd let any Imperial army use a squad or two of GK or GKT as a requisition in any games against Chaos (and maybe DE). And then if the other army is defeated, you roll a die to determine if you need to be cleanesed. If so, the opponent controls the remaining GK until nothing remains. And then I'd up-power the GKs. But I don't play much.
I did love the callback to a previous =][= series. Simple and understated, but effective at bolstering both stories. And it was essentially a free "origin", so kudos for literary efficiency. It was nice to finally see ADB tackle the Wolves (my favorite army) and I loved his take on them. The book was well-structured, and some of the sequences just sizzled. Typically, when something in 40K history is expanded to book form, it tends to lose the aura it had in the smaller size chunks. ADB manages to pay respect to the scale of the events, but add texture and even scope. Events become more powerful under his pen, rather than diminished.
Well worth the read. ADB continues to impress.