Undoubtedly a contender for a notional "strangest book ever written" award, it is set in a fictional landscape where even the fictional nature of the novel itself is open to interpretation and question. First published in 1979, the book begins with a chapter's worth of preface on the art and nature of reading. Things do not become any more transparent with the subsequent chapters in which various emergent storylines are exposed as fraudulent storylines, neat parodies within parodies of the airport blockbuster novel variety are instituted, examinations of various false documents described within it are performed, verfied, discredited, etc, etc. What binds this novel so well together is Calvino's delicate and precise literary style.
The title If On a Winter's Night a Traveler is a good indicator of this novel which is reminiscent of Laurence Sterne's Tristram Shandy. The book commences on a hypothesis of novelistic elements ("If...") on a when, a someone...would do what? According to this book, the entire novel, even its plot, is an open trajectory where even the author himself questions his motives of the writing process. This theme -- a writer's objectivity -- is also explored in Calvino's novel Mr. Palomar, which explores if absolute objectivity is possible or even, agreeable.
See also: self-reference