The Flight of the Eisenstein by James Swallow is the fourth book in the long-running Horus Heresy series by the Black Library. It follows the Death Guard Captain Nathaniel Garro as he witnesses the massacre of his brother legions on Isstvan III and his struggle to pass the message of Horus' treachery to the Emperor. It is a sister novel in some ways to Galaxy in Flames, as it shows the events on Isstvan III from a more distant perspective, and from the point of view of an Astartes warrior who has not been party to the changes in Horus and his turn to the forces of Chaos.
By the nature of the story, The Flight of the Eisenstein was never going to be a happy book, but much of the humour and moments of levity from the previous three novels in the Horus Heresy is absent here. Brother betrays brother; Chaos is on the rise; and Garro finds himself questioning everything in which he once believed. It is a dark, grim testimony of the darkness growing within the forces of the Astartes.
Swallow does an admirable job in taking the events covered by Ben Counter in 'Galaxy in Flames', and providing us with the alternative view - in fact, the scenes in which Garro watches in disbelief as Isstvan III is destroyed far beneath him are some of the most powerful and moving in the series to date.
There is also a nice turn in discussing the nature of new vs. old traditions within the Death Guard Legion, which echoes the over-riding theme of Lodges and following a new belief shown in the whole Horus Heresy series. Garro is one of the oldest-serving within the Death Guard, one who was born on Terra unlike many of his battle brothers. He adheres to many of the old traditions and finds himself somewhat outcast within his own Legion.
I also enjoyed (although I'm not sure "enjoyed" is quite the word!) the portrayal of warriors who are unable to fight any longer. Here we have Garro, defiant in the face of injury; Voyen, unable to face the idea of being part of war anymore; and Decius, who chooses a very different path. In each case, Swallow shows how a fighter might respond to the idea that he can play no part in the role that he was born to. All three storylines were written incredibly well.
In The Flight of the Eisenstein, the massive and far-reaching events covered in the first three novels are brought down to a much more micro level. Much of the novel takes place on the Eisenstein itself, and has an incredibly creepy and claustrophobic atmosphere because of it. Adding in a glimpse of the Warp and how Chaos affects the Astartes only increases this.
My main issue with the novel is a matter of characterisation. The Death Guard Legion is not the most charismatic, and they feel a little mundane on the pages. Compare this to the Luna Wolves/Sons of Horus, and the novel becomes somewhat dry. I don't think this is necessarily a fault of Swallow - in fact, I think he portrays these Marines well.
What is a fault of Swallow's is the fact that at times there was little to differentiate the individual characters within the Legion. Apart from Garro himself, Decius and Grulgor - all of whom have a large role to play in the novel - the rest of the Marines are interchangeable and difficult to identify.
All in all, though, this is a very solid entry into the series - dark, forbidding and challenging to read for all the right reasons. Good effort.