A Wizard of Earthsea
Le Guin is a master of the craft, of course, even when turning something as ephemeral as a fantasy young adult novel. Starting from the premise of “what were Gandalf and Merlin like as young men?”, Le Guin traces out the early career of Ged/Sparrowhawk, a powerful mage in a deeply historied archipelago where knowing the true names of things gives you power over them. A prideful boast unleashes a terrible shadow into the world, and Ged has to go on a journey of self-discovery and mastery to restore the equilibrium. As elegant and simple as Shaker furniture, this book is a masterpiece for all ages.
UPDATE: Better on every reread. Le Guin is the GOAT