I favor the Mechanicum for their aesthetics and lore, so I was excited when this came up in the Heresy queue. It was rather good, though it came to an abrupt and muddled end. Perhaps it would have worked better as a two-volume exploration of the events on Mars, but I have no idea how the scheduling for the production of these books go. I imagine it is breakneck and harrowing.
Sidenote: I do not like Toby Longworth's reading. It has a distracting and annoying explosive rhythm to it, similar to William Shatner's classic Captain Kirk. Longworth does have an excellent American character accent, though.