Richard Green writes to me:
If the likes of Hitchcock and others could turn works that were mediocre in literature into great films, I wonder what mediocre films could have been great literature.
The point is not to come up with a list (though some of you will) but rather to ponder what we can learn about literature as a medium. He continues:
…literature adapted from films is almost (and this is a hedge because my experience says invariably) hack work, rushed and held in the lowest regard...Is it because literature is the elder medium, and has a higher status which would prevent condescension to recognising a prior from another medium? Is it because creation is more personal to a individual writer than the inevitable collaboration of film, and so they are loath to allow others’ work in?
Movies need (at least) a plot and a script and that can be taken from a book, with results of varying quality of course. But I do not have an equal understanding of which factor of production is scarce to writing a good novel. Do professional writers benefit more from showing originality in creating a world and also creating a language? There is plenty of fan fiction based on Star Trek and the like but few professional writers take this same tack.
A simple default hypothesis is that movies are more powerful and more real than books. So a movie based on a book won’t necessarily be overwhelmed by its source but a book based on a movie will be. Of course there are many books adapted from oral tales so maybe it is the addition of the pictures that is so overwhelming. I know only a few books adapted from paintings, most notably Gert Hofmann’s excellent Der Blindensturz.