I was struck by the similarity between the two of them, with the ending of Promethea and the idea behind Neomicon being dark reflections of each other.
Promethea's ending is an apocalypse of the mind, whereby everyone in the world undergoes an event in which they "wake up" and effectively start to experience the world the way that Alan Moore does. The event itself is a magical increase in awareness (similar to the ending of The Invisibles in many ways) in which Promethea allows people to see that their perceptions of the world are not the world itself, and that time and space are just ways of looking at something that is both simpler and more complex than they really think. The end effect for many people is an awareness that the universe is sentient, and that they are loved.
Neonomicon is also about a world that's simpler and more complex than people think it is, where a few characters experience an extrusion into their sheltered perceptions from the True universe. But in this case the true universe does not love people in the slightest. It is the world of Cthulhu and Nyarlhotep, where reality is just too big for people to take in, and attempting to drives them insane. Neonomicon's idea that the world we live in is 4-dimensional, and that the Outer Gods are ourselves in the future (which is also now, due to time being one of these dimensions) plays nicely into that (and this is the point that ties in nicely to Grant Morrison's Invisibles, as well as his earlier superhero work Zenith*).
This is one of the key differences between science fiction and horror** - they both deal with an encounter with the unknown, but in most science-fiction we defeat the unknown (or use it to our advantage) in horror the unknown is there to be fled from, repelled, or (if the protagonists are particularly unlucky) transformed by.
This was the thesis of The Courtyard, the short story that contains the seed for Neonomicon***, that exposure to the very language of the Outer Gods was enough to drive people insane - once you understood a few concepts like "Dho-hna" or "Wza-Y'ei" you became functionally different, and your actions were not comprehensible to ordinary humans.
Of course, by the end of Neonomicon the transformation of Detective Brears is completed with her still retaining what seems to be a fair chunk of her sanity, but also happy for the world to become somewhere terrible to behold, because she believes that people deserve it. Which, considering the awful things she goes through, doesn't seem that unreasonable a proposition.
This idea of transformation ties back to something which seems to have happened to a few writers. Philip K Dick, Grant Morrison, Dave Sim, Robert Anton Wilson, Alan Moore, and a few others seem to have at some point experienced _something_ and then spent years trying to find ways of trying to explain it, even though the experience itself only makes internal sense.****
If one believes in a positive universe, where a caring creator/pervading spirit wishes us to be happy then the experience is likely to be seen as a positive thing. If one feels more negatively about the universe then paranoia and a feeling of general horror seem to be the order of the day.
Reading these two so close together gives an interesting look at one writer showing both sides of the same coin, and that was fascinating.
*Which I wish someone would reprint.
**Yes, I'm generalising wildly here.
***It was converted to a comic a few years ago, and the remainder of Neonomicon was then written as a four parter when Alan Moore had a tax bill due. Also, that's a terrible pun.
****Being the kind of person I am, I think that the something was an event in the brain, and almost certainly caused by drugs in those cases. It seems that similar events can be caused by praying a _lot_ and by meditating, both of which can cause altered mental states.
Original post on Dreamwidth - there are comments there.