On the plus side, I found this a fast and undemanding read. The protagonist – Nathaniel Garro – reminded me a lot of Loken from the previous 3 books, which is slightly troubling for the rest of the series.
On the negative side of the ledger, starting the book before the events of Isstvan III was annoying and it felt like half of the book was playing catch up. In terms of the broader story arc, I didn’t feel this book advanced the story that much. Yes, the Emperor has been informed of treachery, but in plot terms, that’s a chapter not an entire novel. And after four books, I really feel we should have a far greater understanding of the forces of Chaos lurking in the warp. Or perhaps I’m just looking for more depth in a story-line that simply can’t deliver it?