The Man Who Was Thursday: A Nightmare (1908) is the most renowned and critically acclaimed novel by a very prolific author. Equal parts mystery, suspense story, allegory, and farce, it is considered a classic of the spy genre while at the same time almost constitutes a genre of its own. The Man Who Was Thursday has fascinated readers for nearly a hundred years now, largely because it does something that mysteries rarely do: It repays rereading, each time revealing new meanings and nuances, while its jokes never become stale.

The hero, Gabriel Syme, is Chesterton's ideal of the virtuous Common Man. He must infiltrate and try to thwart an anarchist cell, at whose heart is the mysterious and ambiguous Sunday, a man whose powers seem almost godlike. Syme's mission leads him through the back ways of Victorian London and on a wild chase through the French countryside, an adventure at once madcap, surreal, and cosmically important. More than just a charming tale full of Dickensian characters and a mysterious man who was supposed to be "Thursday," The Man Who Was Thursday asks the darkest question of all in relation to human race: Will we survive? It is a question as relevant at the start of the twenty-first century as it was at the beginning of the twentieth.