You read it in collected form at 15. I read it in serialized form when it first appeared. Blew my nine-year-old mind, especially the ending.
It was also my introduction to Walt Simonson's art which was totally different than anything in comics (especially the relatively staid DC Comics) at the time. To this day, he's one of my top ten Batman artists largely based on this story.
Too bad DC animated doesn't adapt this, using Simonson's art as the storyboards/character designs.
