It was 1966 in Madison, Wisconsin. Teens fascinated with self-proclaimed guru Spencer Mallon participate in a ritual with him. By the time it's over, one has disappeared, one is insane, one is going slowly blind, one has been literally torn apart, and all have been altered. Years later, the only member of their group of friends who wasn't there, now a successful writer, tracks down his old friends and gets them to tell their versions of what happened that night.
Recalling Rashomon, each story differs in the details, and those differences give us insights into the characters telling the story. Also like Rashomon those differences and what they reveal about the characters are more important to Straub than illuminating exactly what happened that night and what it all means, so if you're only interested in linear storytelling with concrete conclusions, you'll want to look somewhere else. But if you're a "the journey is more important than the destination" type, you'll find a lot here to enjoy.
The prose itself is fluid without being flowery, and the pacing is consistent. The characters are both the greatest strength and the greatest weakness of the novel.
Some characters shine: bitter, empty Meredith Bright is just as chilling in her way as nascent serial killer Keith Hayward.
Howard "Hootie" Bly is a revelation. He was so undone by the incident that he retreated into madness, able to communicate only by quoting from books, mostly Hawthorne. Hootie's innate gentleness and goodness is as clear and effective as Bright's emptiness. Straub's affection for Hootie is clear, and it's well nigh impossible not to agree.
Because so much of the information is filtered through one character (Harwell, the writer), it's sometimes hard to get a grasp on the others in the group, or to know if a description or insight is objectively true, or merely Lee's opinion. This adds yet another Rashomon-layer to the story, but leaves the reader adrift.
The other big problem for me was the character of Spencer Mallon. We're told about Mallon: he's devilishly handsome, he's ridiculously charismatic, he inspires devotion bordering on adoration from the group; but barring a couple of glimpses by Lee that may or may not be Mallon, since he never met him when they were young, we never experience that charisma for ourselves.
This may have been a conscious choice by Straub; we're in the same boat as our narrator, who only knows Mallon by what he's been told. But given that Mallon is another survivor of the incident, one can only wonder what his version of that night would look like.
So if you're looking for a straight-up, good-vs-evil, good wins in the end horror story, you probably won't be happy with what you find here. But if you're interested in good writing, layers of meaning, and a meditation on how what we see and remember often says more about us than about what we've seen, then you should give A Dark Matter a look.
Check out the RevSF interview with Peter Straub.