Wolf In White Van is one of those novels that leave behind a haunting after-image, its avoidance of a conventionally cathartic resolution both a source of frustration and an assertion of its power.

This is the second novel by John Darnielle, already an acclaimed singer and lyricist in the American indie-folk group The Mountain Goats, and it will evoke strong feelings, one way or the other. It's short on plot, but explores minutely the mind of a youngish man from South California named Sean Phillips.

Isolated, obsessive, his inner life defined by the Conan stories of Robert E Howard, Sean was disfigured by what's ambiguously referred to as an "accident" when he was 17. His face has been partially reconstructed, but he tends keep himself to himself. He runs a postal role-playing adventure game called Trace Italian, which takes place in the irradiated post-apocalyptic landscape Sean constructed in his head to keep himself sane during his months in hospital. Players send him their moves through the mail and he posts back updates on their progress through the game.

Being the gamesmaster, Sean is in the privileged position of seeing the decision-making process in action and learning about people by studying their choices. But it's a double-edged sword. He carries too the terrible burden of what happened when two obsessed teenagers, Lance and Carrie, took the game too seriously and actually ventured out into the wilds of Kansas, where Trace Italian is set. One died of exposure and the other almost followed.

Sean's own choices - the sequence of events and decisions that led to him losing half of his face - is obviously the point to which the whole narrative is inexorably heading, but Darnielle doesn't want to let us have anything too easily. So while Wolf In White Van has at least a pretence of forward momentum, Darnielle acts the part of the co-ordinator of a game which, like Trace Italian, no-one is seriously expected to play to completion. Like all "difficult" fiction, this novel carves out a niche for itself by refusing to pander or provide easy answers.