Paul Beakley, can I recommend you also look at Graham’s “Stealing Cthulhu” (http://thievesoftime.bigcartel.com/product/stealing-cthulhu-pdf), which he published in 2011?

I’d (rudely) suggest it’s the precursor to this Cthulhu Dark (and, indeed, contains the ruleset), and there is a going to be a lot of crossover.

However, the breakdown of a host of “classic” Mythos beasties, and the other writers’ notes in the PDF are a marvel.

To my mind, Cthulhu Dark is probably better, having had 7 years to rethink, expand and polish his thoughts, but if you are looking for more Cthulhu Dark, I would get “Stealing Cthulhu” in a hearbeat.