Favorite living American author you'd label as "unsung"?

By "unsung" I don't necessarily mean "unknown," since that's too subjective of a term (you, for instance, know them, don't you?). I just mean an author nobody else you know has read, one whose books you'd be shocked to encounter at a major bookseller like Barnes & Noble, Books-A-Million, etc.

For me, the answer, hands down, is Thomas McGuane. Every time I read one of his books I'm baffled he isn't considered among the all-time greats of American comic literature.