“Among the nominees for this year’s National Book Award in fiction, which will be presented next Wednesday, is a book that some have complained is not exactly new: Peter Matthiessen’s ‘Shadow Country,’ published by Modern Library, which is a one-volume compilation of three novels that Mr. Matthiessen published from 1990 to 1999.” But Matthiessen does appear to have substantially rewritten the text, so some wonder what all the fuss is about.