Is Toni Morrison's Beloved "the single best work of American fiction published in the last twenty-five years?"
Yes, it is.
Yes, that is, if you accept the verdict of a (very small) plurality of "a couple of hundred prominent writers, critics, editors and other literary sages" whose views were solicited by the New York Times.
You may disagree with their assessment or you may not know much about the novel. In either case it should be worth your time and effort to read Stephen Metcalf's Slate article on the novel and its merits.
--Marshal Zeringue