"First: This is the third book in the Ultramarines series, but at the same time it is the second book in the Iron Warrior series. So, you have to read the books in the following order 1)Deathbringer, 2)Ultramarines, 3) Storm of Iron, 4)Dead Sky. If you don't read Storm of Iron 3rd, then you will not understand the people and events that this book refers too, and you will feel that the development of the Chaos forces, as characters, are lacking.
Second: There are indeed some errors in this book that should have been corrected in the editing process. But, if you read the other three books, then you will want to finish the fourth book, so just live with the errors. They are not too many, and the story is pretty fast paced, so I suggest you just ignore them and enjoy the book.
It's not the best of the series, but if you enjoyed the first three books, you will enjoy this one also."