Tolkien was pretty clearly INTP, especially when you compare his thought process and writing process to CS Lewis, his close friend.
(To rule out INFP, compare Tolkien to INFP fantasists like Terry Brooks or Neil Gaiman or Madeleine L'Engle, or to INFJs like Guy Gavriel Kay or Stephen R. Donaldson or Piers Anthony.)
Did I mention Ursula leGuin as an INTJ writer? I am pretty sure of that one, especially having attended a speaking session of hers and meeting her briefly, watching and listening to her interact.
I have at least one Barbara Sher book at home, I remember enjoying it / finding it helpful in some ways.