Just finished reading the PDF. This book is fantastic and it feels like a thoroughly encompassing way to get your players mired in a frightening mess. The NPC art is superb and frankly even the normal people have an unsettling look about them. It's clear that even with the deadliness of violent situations, most of the threats to sanity will lose only 1 SAN at a time, making the slip into madness feel slow but inexorable. The linking of curiosity to danger has never been more direct in a COC/Delta Green book.
The plot really shines in a section where players think they have escaped the surreal locations for a second time, only to find themselves still hallucinating under the influence of the King - the example hallucinations are just chilling. Also, the way the author has found to deal with the narrative problem of the players being wanted and caught by mundane law enforcement (not exactly supernaturally scary in their own right) is very clever. The callbacks between different times and places, and spaghetti of connections between NPCs, is incredible.
The only thing it could use but doesn't have is a bibliography or list of influences/references, would be nice to see the recommended stories by Chambers, Borges, etc. in addition to the clear recommendation of a classic public domain demonology text.
There is an appendix of side-character NPC encounters that is worth the price of admission and would fit right into any modern horror/magic setting such as Unknown Armies.
(I reviewed this a couple weeks ago but it was turned into a "Discussion" so here is the review again)