For those who aren't familiar with it, Abyss recounts the dogged pursuit of a massive Word Bearer's ship on route to destroy the Ultramarine home world of Macragge. The Imperial forces are a mish mash of legions and it was interesting to read the dynamic between them. Getting to know the Astartes and to see how crafted and varied their personalities were was really enjoyable, it was also good to see some of the traitor legions not being traitors (especially the World Eaters who have never gone down well in most other narratives!)
Space Wolves feature heavily and the interplay between them, the Ultramarines and a captain from the Thousand Sons was great, the Space Wolves loathing of psychic 'witchcraft' is palpable and the staunch bearing of the Ultramarines is also much in evidence. There is a lot of heroism in the book and a great deal of sacrifice, though I found that I was not as attached to these characters as I was to say, Nathaniel Garro in Flight of the Eisenstein or Captain Ventanus in Know No Fear.
Surprisingly I have no desire to build something from the book which must be a first... I've recently bought a 1,200 Raven Guard army after reading Deliverence Lost and I've built a Nathaniel Garro after reading Flight.
As always I have too much to do...