Maybe I heard something about this years ago; maybe the title was intriguing. I found the book pretty entertaining, if obscenely vulgar throughout. I don't know that I'll read the sequels (not that I knew until just now that there were sequels), though I am interested to know what happens to David and Amy (I appreciated that part of the ending).
I also liked that, for all the supernatural/spirituality of the novel, it never openly disparaged beliefs.
It was strange that while I would often go to sleep listening to this...I never experienced any nightmares from doing so. Though near the end was probably the creepiest concept that it brought up - if the "shadow people" (or, frankly, demons or whatever) can erase people or things entirely from history - what all might have changed? One character brought up that "as of a month ago" no such things as video games existed. Now, suddenly, though, millions of kids everywhere are staring at their TV's, gunning down virtual people with no emotional reaction... as if they're being trained. Now there's a scary concept.