This was my response; movies and music from my childhood are often enjoyable, but nothing has hit me as hard (and repeatedly) as Shadowland.
Peter Straub, Shadowland. First copy was a birthday gift? in 1980, I remember reading it while cooped up at home with bronchitis in between raging at the final days of the campaign leading to Reagan's election. I'd just turned fourteen, but knew he was going to be bad news from my POV, and I was pissed that I couldn't vote. Last read in 2008 when I got a new copy after it being lost or not returned again (I think this is my fourth copy, but I can't be sure).
I have read and enjoyed many of his other books, but Shadowland is the one that still has the power to make me want to change the world, and the only story that makes me believe, at least for a moment, that magic exists. I can suspend my disbelief and enjoy books with magic, but Shadowland doesn't require any suspension at all; 20+ years and over a dozen re-reads later I still believe when I read Tom's story.
What about you? Comment here, or in theferrett's original post and leave me the link...