[TOMT] [1970s-early 80s] [Book - young adult thriller, probably] Obscure pulp paperback thriller about a teenage boy stalked by a creepy man who lights the boy's bed on fire (but it may turn out that the boy set the fire himself).

The creepy man may have been real or "all in his mind," I don't recall. EDIT: I think the man was real but it was unclear whether or not he was a villain: the boy knew the man in some way and didn't trust him, but I don't remember if the distrust was all in his mind.

A turning point of the story was the boy's realization (or admission) that he had set the bed fire himself, due to some kind of mental trauma/anguish/illness, the details of which I don't recall.

It was relatively short, probably not much more than 100 pages paperback. Geared towards young adults or maybe older children. Dark cover which, I believe, had a picture (or silhouette) of the stalker looking burglar-ish, maybe wearing a knit ski cap (EDIT: or maybe a mask of some sort?) -- something that gave him an unmistakeable a burglar-villain look. The man was middle age or older.

I don't think it was written by a particularly famous author or that it was a well known book (but I could be wrong). I think it was just a cheap bargain-bin kind of paperback.