This novel is set in vaguely modern Britain (the precise date would be a spoiler) and deals with a charater who discovers that his upstairs neighbor believes himself to be the Man in the Iron Mask, both of history and of Dumas' novel. The action follows the character's increasing involvement in and frequent resistence to this madman's fantasy world. Likewise the character is drawn into the madman's family life. Without getting specific, the novel is about the "cantagiousness" of madness. This is a serious issue, but this is a modern novel and is mainly interested in the question for "effect" and not in any philosophical way. It is well-written, and those who want no more from a novel than literary in-jokes and surreal effects should find it thoroughly satisfactory. For my tastes (and I do like the surrealism of Borges and Kafka, for example) the book did not seem to be about real people; nor had it anything interesting to say about Dumas; nor anything interesting to say about the historical Iron Mask. I came away from this book feeling that it had been a pointless exercise.