Sphere - now that brings back memories of the first time I read that.
I remember sitting up in my lounge room reading it at about 3:00am. Thunderstorm raging outside.
Just as I got to the exciting/scary bit (don't want to spoil anything here) I heard a noise outside the window. I gingerly walked over to the curtains and pulled them aside quickly just as a bolt of lightning struck. I saw a 'man' looking at me from the other side of the window and screamed like a girl...until I realised it was my reflection.