What’s an awesome book you’d never heard of but found randomly as an old paperback in a secondhand bookstore, under a bench or couch, in your grandma’s storage shed, at a swapmeet, in a doctor’s waiting room, etc, and decided to give it a shot?

I've come upon some of my favourite works completely by accident just stumbling across an old copy by the roadside of life.

Eg, Tigana, The Champagne Spy, Rogue's Gambit, Gormanghast, Dunsany's Book of Wonder, Den of Thieves, All the President's Men, Thomas Covenant, Prince of Tides, Conspiracy of Dunces, etc.

What have you chanced upon randomly and were delighted you did?