The invisible / Mats Wahl ; translated from the Swedish by Katarina E. Tucker.

Enhanced descriptions from Syndetics:

One ordinary Monday morning in May, Hilmer Eriksson walks into his high school classroom and discovers that he has become invisible. No one can see him, no one can hear him. In fact, a police detective named Harald Fors arrives at school that very morning to investigate Hilmer's disappearance. The boy has no idea what's going on, but he's frightened, and he's starting to forget things - including what happened to him a few nights earlier. Detective Fors suspects foul play, and those suspicions lead him - trailed by the ghostlike presence of Hilmer - to a group of skinheads. These unpopular, disaffected kids are very vocal about their Nazi sympathies. But how does Hilmer's life intersect with theirs? As Fors scours the village and interviews area residents for clues, he begins to piece together the puzzle of Hilmer's disappearance. Meanwhile Hilmer waits, silently, to discover what has happened to him.
In this riveting mystery set in northern Sweden, Mats Wahl deftly alternates between the policeman's and the victim's points of view, as the story of a missing-persons case shifts with a sad inevitability into a heartbreaking murder investigation.