An abridgement implies that the plot is central to the story, when clearly the style, pacing and other elements are important, particularly if we're talking about something that is viewed as a "classic". While plot may indeed be the central point to popular fiction, the whole point of "good literature" is that we don't just enjoy the story, but how it's told.

Of course, if the author agrees to edit down a work and signs off on the edit, then we're in a different situation. At that point the person responsible for the work in question can decide whether an abridgement compromises the integrity of the book as a whole.