This was one of the most demanding books I've read this year, and I honestly had to sleep over how to rate it.
On the one hand, Nabokov's style and language are brilliantly impressive. On the other hand, the narrative voice and the story as such are horrid, and increasingly so as the book develops, both of which is almost too convincing for comfort.
Humbert Humbert is, frankly, a villain who would like to fashion himself as a victim, variably that of circumstance, and of Lolita. The whole book is a defense plea on his part, swaying between the slavery to his cruel mistress, the woman-child, and his unconvincing regret of ruining the child-woman. His basic assumption seems to be the cliche of sex-offender-defenses: "She wanted it, or else she wouldn't have been that lascivious around me all the time." Humbert attributes Lolita with a lot more adult sense and comprehension than anyone could expect of a child of twelve (at the beginning) to allow himself to be the victim of her seduction, and the lover treated cruelly and unfairly when he only wishes Lolita to be happy with him. There could, of course, never have been informed consent, or a love between equals here. Humbert tries to frighten the child into secrecy and acceptance after having made himself the only attachment figure available.
I felt angry most of the time reading his confessions, never knowing whether the narrator was actually fooling himself or just putting up a show to fool the reader about his view of the affair.
It is the most amazing thing that Lolita manages to find her way to a more or less normal and happy life once she has escaped from Humbert and her rescuer likewise. And it is Humbert's only redeeming quality that he does not ruin this small patch of normality for her.

It is absolutely frightening and amazing at the same time to see how very convincing Nabokov developed Humbert's written confession. This book cannot fail to draw strong emotions from the reader, and it would possibly have been unbearable to read if one had had to see Lolita during her ordeal without the filter of Humbert's point of view.