Warrior Brood is the first book related to the Deathwatch (elite Space Marines picked from all chapters to work for the inquisition in small kill-teams), written by the apparently infamous C. S. Goto.
And well, while the book delivers action, you must indeed have to allow quite a few mistakes, inconsistencies (with the Warhammer 40k world) and in general inventions of the author.
Some units are wrongly described (Tyranids mostly); others have new ultra-powerful habilities not found in the game; Space Marines appear to be really weak in general...
The book relates a Deathwatch detachment sent to a sector under attack from a Tyranid hive fleet, but where some things are not as simple as they seem.
A dumb successor chapter is introduced, and some Deathwatch marines are from lesser chapters or directly from the Blood Ravens (coincidence that this author wrote the book Dawn of War, based on the videogame that invented this chapter). Allows for some specific argumental decisions but in general I miss more realistic chapters.
As I said the pacing is quite good, you won't miss action and if you forgive the heresies related to WH40k lore, the book is not a bad reading, but neither impressive.