I was really looking forward to this book, as the Word Bearers were one of the original legions that I know very little about. My only previous experiance was with The Battle For the Abyss, and that wasn't really a Word Bearer book.
I enjoyed this book a great deal. It was different from many of the other Horus books in that we have a main character that isn't a stand out against the fall of his legion like Garro from the Death Guard, or even someone who is convinced he is doing what is good for the Imerium as Ahriman is in A Thousands Sons. Here we have a main characer and a whole legion that are sure that the Emperor is wrong, and they are hell bent on finding the true gods that the Emperor denies, even if those gods are the Chaos Gods that we all know and love.
The only part of this story I really didn't like was one scene where Erebus and Kor Phadon convince Lorgar to abandon the way of the Imperium and that the legion should seek out the old gods. It all takes place in the space of about 10 or 15 pages. It seemed way to fast.
I did, however like the back story behind the fall of the Word Bearers. Especially the scenes with the Emperor. I believe this is the first time where we've had the Emperor in one of the stories (except for the short story in Tales of Heresy). It was awesome to see a whole legion including their primarch humbled by the Emperor.
We also got to see a bit more of the Custodes and their bad-ass-itude. Those guys rock!
In the end, as with all Horus books, we know what is going to happen, but it is the path that leads us to the end that is worth the trip.
I am very tempted to give this five possessed Space Marines out of five, but it doesn't quite make it. If I were to give "half points" I'd do that, but we'll have to settle for four out of five.