Blood Reaver is the sequel to 'Soul Hunter' and follows the same characters from the Night Lords Chaos Marine Legion. As far as Black Library books go, I would say this is among the best. The title, Blood Reaver, refers to Lord Huron Blackheart of the Red Corsairs, a powerful group of renegades who the Night Lords are forced to deal with.
Aaron Dembski-Bowden's writing is very natural and easy to read. Unlike many of the other Black Library authors, he has a diverse and evocative vocabulary, so he can tell his story without the language or plot getting repetitive. His characters are also a bit more subtle and have more depth than most, and he succeeds in making aspects of several characters, including the 'post-human' Space Marines, relateable.
In short, if you find the villains of the Warhammer 40,000 Universe interesting, you will probably enjoy this book.
I actually enjoyed it more than Soul Hunter, since the characters seemed to me to be less morose. Granted, the characters were basically already introduced in Soul Hunter, so there is less exposition required.
Stop reading here to avoid any details about the plot.
My one big complaint about many of the Black Library books is the characters' motivation, which is often just assumed or glossed over very quickly. Dembski-Bowden does an excellent job with his human characters (and did a great job in 'the First Heretic' with the Word Bearers) but it is hard at times to figure out what the Night Lords are trying to accomplish.
I appreciate that part of their struggle is finding purpose after their Legion was shattered by their Primarch. However, Talos and the other key characters have been living for more than 10,000 years by the time this story is being told and it's unclear what exactly they are fighting for at times. Consequently, it is hard to judge whether they are succeeding or failing.
I think I feel this way in part because I am not sure how I feel about the ending of Blood Reaver. There are certainly several dramatic events in the middle of the book, but the net effect on the principle characters is unclear at the end. Even so, a very fun read.