Under the Volcano by Malcolm Lowry

"Lowry's masterpiece" about a fateful Day of the Dead in a small Mexican town and one man's struggle against the forces threatening to destroy him (Los Angeles Times).
In what the New York Times calls "one of the towering novels of [the twentieth] century," former British consul Geoffrey Firmin lives alone with his demons in the shadow of two active volcanoes in South Central Mexico. Gripped by alcoholism, Geoffrey makes one last effort to salvage his crumbling life on the day that his ex-wife, Yvonne, arrives in town.

It's the Day of the Dead, 1938. The couple wants to revive their marriage and undo the wrongs of their past, but they soon realize that they've stumbled into the wrong place and time, where not only Geoffrey and Yvonne, but the world itself is on the edge of Armageddon.

Hailed by the Modern Library as one of the one hundred best English novels of the twentieth century, Under the Volcano stands as an iconic and richly drawn example of the modern novel at its most lyrical.