Gav Thorpe has been steadily building his vision of the Heresy era Raven Guard with the audio drama Ravens Flight and short story The Face of Treachery (featured in Age of Darkness). Now he is given a full novel to 'stretch the wings' of this Legion.
Deliverance Lost is a solid addition to the Heresy series, whilst it doesn't soar to the heights of say A Thousand Sons it certainly doesn't nose dive like Descent of Angels.
The novel has a lot going for it, Gav has engineered a fitting feud between the Raven Guard and the Alpha Legion, the two most clandestine of the Space Marine Legions; providing a lot of information on the origins of the Ravens 'gorilla warfare' doctrine and expanding on the Alphas shadowy and ultra covert methods.
He also really fleshes out the character of the Primarch Corax, with flashbacks providing a wealth of detail on his origin story, making him by far one of the most 'human' of these demigods, whilst going up to eleven on the super human abilities dial!
We are provided more insight into the Primarch Project and this story actually moves on (at least in the case of these two Legions) from the rut that Isstvan has unfortunately become.
It's not without fault, the pace is a little off, with a few threads feeling underdeveloped and a rushed ending that tidies things up neatly but left me feeling a bit underwhelmed following such a great build up.
Still I think Gav Thorpe, like the Raven Guard and Alpha Legion, takes the long view; this isn't a 'legendary battle' of a book, but another in a series of actions that serves to strengthen the series objectives as a whole.