BOX SET REVIEW John Mellencamp On the Rural Route 7609 [Mercury/Island/UMe] When it comes time for the box-set treatment, most artists are content to line up a few discs’ worth of hits and rarities and let ’em fly. John Mellencamp is not like most artists. On the Rural Route 7609 is a four-CD collection that sets out to tell a story all its own, tracing connections among its songs and emphasizing its author’s current attitudes and concerns...