Here is an essay on films based on previous works, in this case mostly on comic books and TV shows. Rilstone’s conclusion seem to me to be very relevant to Tolkien films. He actually starts talking about his feelings about a new actor playing Doctor Who in place of Matt Smith but then goes somewhere else.
Go to
http://www.andrewrilstone.com/search...max-results=10 .
Then search on
Hello, I Must Be Going .
Faith that the film is going to be a magnificent version of the previous work, exactly as we imagine it.
Revulsion when news comes out about what the film-makers are going to actually do with their source, or on seeing the completed film.
Retrenchment to the opinion that no-one who knows anything ever expected a purist film and all that matters is whether the film is good on its own terms.
Rilstone does not mention that many fans do not jump to the Retrenchment stage, but remain revolted. That may be because the film is so bad that most cannot now support it, even though they would like to.