The Skull is like a perfectly-paced rollercoaster.
Philip K. Dick, oft-referred to as PKD by fans, is one of the great pillars of American sci-fi and one whose influence you've likely felt, knowingly or not. His stories have received countless adaptations and re-imaginings, and for good reason: the addictive cycle of intriguing questions answered by mind-blowing reveal is evergreen.
The Skull is one of Philip K Dick's earliest-published works (not including the novel manuscripts released posthumously). It was originally published in the September 1952 issue of sci-fi publication If, and a scan of its charmingly of-its-time cover is included in the media-enabled formats of the story found on Project Gutenberg.
Because so much of PKD's short stories rely on the cerebral build-up to an earth-shaking revelation, I'll forgo any details about the contents of the story itself. It's short and easy-to-read, and can be finished in a single sitting without much difficulty. In fact, if you enjoy this story, I'll also point to PKD's Beyond Lies the Wub as a similarly tight-paced read (it's even shorter!), which also came out in 1952.
I'd gush more but I don't want this recommendation to be longer than the story it's about. Find (and read) The Skull by Philip K. Dick at Project Gutenberg here. The previously-mentioned Beyond Lies the Wub can also be found via Project Gutenberg here.
That's all. Go read!