I feel for authors whose books are made into bad movies

I very much doubt that many of the latter-day living writers who get fat checks to turn their opi into films much care (Dan Brown, anyone? Stephanie Meyer? The Fifty Shades of Sh*t author?). They're probably laughing all the way to the bank. And lord knows, a crappy film adaptation would never put me off of a book I had any interest in reading. You expect the average major film production to dumb down anything it touches the better to market it to the lowest common denominator audience; otherwise it would, in most cases, hemorrhage money at the box office.

That's a good point, that on occasion, a film by a genuine auteur (and in the cases of The Godfather with Coppola, and The Shining with Kubrick, I count them as exactly that--auteurs who genuinely re-imaged and even re-wrote to some degree the source material, in order to turn out films that had actual artistic heft) can ennoble a book that was nothing much more than pulp originally, and have the unintended consequence of giving a spurious quality reputation to a written work that certainly didn't deserve it otherwise (Jaws, while hardly a film of high-art pretensions, can in some respects, be included on that small list). But the instances of this are rare, and far more often it's the work that has literary merit that's transmuted into junk for the screen. Nowadays, the most frequent occurrence is the work that was never anything but junk on either the page or on film.