Taking the story from the essay we read, we are shown LaRoche walking through a swamp looking for an orchid. This scene, which is narrated by Orlean, is about as much of the essay we see adapted. From that point on most of the stuff seems to come from the actual novel, of course until the turning point in the film. The second Charlie allows his twin to look at his script for advice, we get all the Hollywood cliches one after another. Not only does the movie play with it well, but on the surface makes it seem as though they aren't even making fun of them all. The events happen, and even though a few seem a little over the top, it feels more like a movie general audiences would expect. From things like car chases, drug use, character death, and some moving revelation, it's all there. It's amazing how Kaufman is able to integrate these cliches as to parody them but make them fit with the story.
This is one of the best written movies I've seen. Also, it is one of the few movies Nicolas Cage is in that he does well, and he deserved the Oscar nod. It has an interesting mix of real life happenings and fictional characters/events. Adaptation is the kind of movie every screenwriter needs to see, whether they plan to adapt something or not. Kaufman delivers one of the most original and self-observant films in recent memory.