In reply to Only a hill:
Yes but is there not an analogy with middle earth here? There is a vast wealth of other material Tolkien wrote on middle earth, and it's that that gives lord of the rings it's depth and sets it apart from other fantasy worlds. But you wouldn't necessarily want to read it in its own right
I can say this with some authority having ploughed through the book of lost tales 1 and 2 many years back...
Not read any of the star wars books, so perfectly happy to be proved wrong, but the films 1-3 struck me as telling a story that didn't need to be told, it was better just being alluded to as back story in the proper films...