Until a few months ago, I did not realize that G. K. Chesterton was a writer of fiction. I knew of his books on such topics as orthodoxy and heresy, but was unacquainted with the fictional works that had an impact on such authors as C. S. Lewis and J. R. R. Tolkien. The first book I read was Manalive. I wrote a review of that book not too long ago.
The Man Who Was Thursday was described by C. S. Lewis as, "A powerful picture of the loneliness and bewilderment which each of us encounters in his single-handed struggle with the universe." It is about a man named Syme, who is employed in the service of the British Police, in a special department, by a special man, to fight against the anarchists of the world. As he infiltrates the inner circle of anarchy, taking the name of Thursday, as each member of the inner ring has a name of a day of the week, he is left wondering, and fighting to determine, who is this man named Sunday?
I've really enjoyed reading Chesterton's stories. There is a certain whimsicalness to his writing as he attempts to discuss serious topics through the use of story, but he does it in a way that the belief system that he is discussing plays a part in the story the way a tent plays a role in the circus.
If you haven't read any Chesterton, this one would be a good place to start. A mix of sci-fi, fantasy, and socio-political drama-comedy!