It was one of the most popular novels of the nineteenth century and Tolstoy called it "the greatest of all novels." Yet today Victor Hugo's Les Miserables is neglected by readers and undervalued by critics. In The Temptation of the Impossible, one of the world's great novelists, Mario Vargas Llosa, helps us to appreciate the incredible ambition, power, and beauty of Hugo's masterpiece and, in the process, presents a humane vision of fiction as an alternative reality that can help us imagine a different and better world.

Hugo, Vargas Llosa says, had at least two goals in...