Second book of the trilogy/omnibus, sending the Grey Knights now to investigate a strange world that has appeared from nowhere and contains dangerous Dark Mechanicum tech-priests and other surprises.
Not bad story, albeith this one being more atipical (the Dark Mechanicum are not very detailed so the author decided some aspects for them).
Some plot parts are very predictable and the topic might not be as interesting as the previous book's one, but one thing I like is that all DK books seem to be settled in a specific "present" timeframe where Abaddon is coming out from the Eye of Terror so the whole universe is in a huge and delicate war with Chaos forces.
Too bad that the "background problems" not advance a bit :P
So, not a bad book but not as good as the first one, you will enjoy it if you like reading about the Adeptus Mechanicus.