I seriously doubt that 99% of all Americans (which should include a good portion of people with Hispanic origins) are so poorly educated that they know no other Spanish book but the Quixote.
But even if true, how could such a fact tell you anything about the value of the book itself as a piece of art, its worth within literature and its influence on Spanish and other cultures?
Just because, to name another example, most Americans might never have read a play by Lope de Vega or have ever heard about him, doesn’t mean they haven’t felt the lasting influence of the artists of the siglo de oro, if only by reading Shakespeare, who stole repeatedly from them.
Many artists we do know stand on the shoulders of giants, who we might not know but who made the art we know possible – because they invented (or added to) the techniques of the art and their subjects.
I don’t know what this is supposed to mean, but I agree that El ingenioso hidalgo Don Quixote de la Mancha is a masterpiece.
First, it’s a very well done book: great prose, interesting and developing characters, a straightforward but complex story line with carefully constructed arcs that have lots of meaning beyond the obvious.
Thus, its interpretation is not an easy task; one school concentrates on its comical side: the Quixote parodies, for example, the at that time well-known genres of the chivalric and pastoral novel; it’s also part of the picaresque novel and triumph over its boundaries.
It’s also a satirical analysis of Spanish history, culture and society; experts like Américo Castro think that the humour in Quixote is a critique against the phoniness of Spanish society and it effectively exposes their deceits by laughing at them heartily.
Others, like Miguel de Unamuno, focused on the heroic aspects of the Quixote; they identified Spain with the book and transformed it into a national symbol.
And there is the epistemological interpretation of the book: one of Cervantes’ themes is definitely the very Spanish idea of la vida es sueño (life is a dream), an idea that was masterfully translated into plays by another author of the siglo de oro: Calderón de la Barca.
Cervantes shows a lot of insight in the question of reality and constructs -– and it’s no surprise that he is often cited by representatives of the Radical Constructivism and similar epistemological schools.
Needless to say that his thinking influenced later authors who have toyed with such themes, like Sabato and Borges but also many other European and American novelists.
To determine the value and influence of a book like the Quixote by polls and lists is pointless … and more than a bit degrading. There is more to art than random popularity.