What, in your opinion, is the (mythical) Great American Novel? At least to date. A “classic,” or a current one–either would be fine. Mark Twain? J.D. Salinger? F. Scott Fitzgerald? Stephen King? Laura Ingalls Wilder?
It doesn’t have to be your favorite book, mind you. “Citizen Kane” may be the “best” film, and I concede its merits, but it’s not my favorite. You don’t have to love something to know that it’s good.
I'll be stupendously unoriginal and go with Huckleberry Finn. It's not my favorite novel (I'd have to go to Dickens for that), but as many others have pointed out, there's something archtypically American about Huck's longing to "light out for the Territory." And the writing itself is fresh and humorous, unlike the mannered, self-consciously "literary" style that characterizes so many "serious" novels today.