Not quite as good as the prior entries (or maybe it's just the hype stabalizing itself), but still very good.

From the end of the last book, I knew I obviously would like to see just what came of Garro following his escape from Istvaan, and was really glad to have this book dedicated not only to that moment, but the events prior too.  It was interesting to see this book spend time on another perspective of the same events from last book, and the author used the fact that the reader would know what was occuring very well in order to build proper tension and deliver a great payoff once more for the same event.

It was a bit off-putting, for the audio version, to hear different renditions of some of the same characters from last book as (I think) this one was done by a different voice actor, but I may be mistaken in that.

There is a lot to like here though from the suspenseful building of the betrayal at Istvaan III to the escape of the Eisenstein through the warp, but I would say that this book, despite having a lot of potential for a varied cast with the Eisenstein's crew, somewhat under-delivers.

The book does a great job of building Garro as a character as well as the characters of other members of the Death Guard, but so too are we introduced to a lot of interesting non-Astartes, including Eisenstein crewmembers and Garro's housecarl, Kaleb.  I was expecting a lot more from Kaleb in light of how he is a perspective character for quite a few chapters, and I was disappointed with how abruptly he died.  It didn't so much feel like a wasted death as I fully understood the themes behind it: this is a war of gods and monsters, and even when knowing you are outgunned, outmanned, to still have hope and courage to fight and die for a greater cause is what makes one a great man, I still was hoping to get more from him.  He has a great arc, great writing, and great dynamics with other characters, and even though his story ends well, I just was sad to see him go.  
:(

However, I did feel like the crew of th Eisenstein itself was somewhat wasted.  A part of me almost wishes that Garro had never been an astartes in the first place but rather the role of the Eisenstein's captain and Garro were combined, allowing for a more non-astartes-centric story, playing more off of the dynamics of the ship crew, because I did indeed want to see more of the crew dynamics.

The story flow was also a bit odd following the Eisenstein's arrival to the Sol system, but I digress.

As for the main plot itself--the escape of the Eisenstein from the Istvaan atrocity, this was great.  Seein the ship and her crew jump from once crisis to the next, forced to make daring decisions with extremely low odds of success, I was reminded of Interstellar's own constant obstacles or those of Star Wars' asteroid field in episode V.  It was tense, exciting, and with the knowledge that in death or life, their warning would reach the Emperor about the betrayal, I legitimately did not know if they would survive or not. 

With this book more than the others, it was easy to identify just how much these books are, at the end of the day, based off of a tabletop game, especially with the description of the chaos marines.  In spite of this, I felt like the author did a good job with how these were explained and justified, because it is no easy task to describe why these chaos marines have devil horns, bile shooting bolters, etc.  This does partially tie in with my other complaint that, though I can understand it for the circumstances of the Eisenstein's voyage through the Warp, I sincerely hope that the majority of the Horus Heresy does not present us with the same total chaos-corrupted goofy-evil chaos marines that we see in this book.  Honestly, I wish that the first instance of chaos marines was saved for far later down the road, but so long as this remains one of the few instances of it in this series, I won't complain too much.

Overall though, great book still, but with one final last comment:

"He couldn't help but think that the events of the last few months were but a prologue to a greater picture."

Really?  

I am now banking on at some point in the series, a conversation going along the lines of:

"What weapons do we have?  How many?"
"Enough"
"I ask again.  What weapons?  And how many?"
"Warhammer...40k."

4.25/5

Oh my god this one would be so easy to adapt into a TV series...James Swallow, your writing *chef's kiss*