I have read both Nabokov's novel and his screenplay for this film and Kubrick clearly read them as well. And then for the better part ignored them. While this method has proven to be successful in his later efforts, here it doesn't work that well.
I understand that the subject matter the story deals with would even be tricky to portray in this day and age, let alone in the time this film was made. But Kubrick makes changes to the story that distance the viewer from the proceedings and it leaves things unexplained, most notably the drive and motivation of Humbert.
In the novel, Nabokov uses the doppelganger motif, in which we are presented with an ambiguous protagonist. He…