This book is well written and very entertaining. It has lots of material that a DM/GM/Referee can draw upon to generate some very memorable campaign moments; it is clear the author spent a great deal of time considering the psychology of creatures and societies that exist in darkness.
For the writing, I give this book a full 5 stars. However, and this is a big one, the art in this book is a hair north of atrocious. Quite literally, it's the worst art I've seen in an RPG book ever. So much so, in fact, that I found it quite jarring when compared to the quality of the writing. I understand what the artist was trying to accomplish with the style, but it failed miserably. There are better ways to convey a sense of dread, fear and the unknown than resorting to senseless scribbles. Art that can be outshone by my 5 year old has no place in a book with prose of this quality.
[3 of 5 Stars!]