Second book about the Deathwatch, this time sending a Deathwatch team to deal with a secret coven between the Inquisition and the Eldar. Of course problems will arise when incidentally the Eldar are suffering attacks from the Dark Eldar.
I actually enjoyed this book a lot. Unlike the predecessor the plot is elaborate and my cons are only related with background (once again) and some plot "convenient situations" unlikely to happen.
C. S. Goto keeps using minor chapters and the Blood Ravens as main ones, but you can easily forgive about it (except for the librarian's "special powers").
Some of the Dark Eldar background (sadistic culture and mixture of lust and masochism) is well represented, and the Space Marines have an additional problem: Dealing with enemies (Eldar) by their duty when they hate them.
Also has nice unexpected plot changes that keep you reading on and on.