Heart of Darkness
I must have been in high school when I first read Joseph Conrad's Heart of Darkness (1899). It's unlikely I would have happened across it on my own. I probably also tried to speed read through it. I certainly missed let's see, the plot, the prose, and the point.
Not so this time around. What an absolutely astounding piece of writing. Even after reading all the accolades and many analyses, even after seeing Apocalypse Now umpteen times, it was a first time experience.
And, even now, it is relevant. So, so relevant.
It's only about 90 pages long. Highly recommend.