Having just read Lolita, I thought it would be interesting to read a more modern take on such a difficult subject, albeit with genders reversed...
It's the story of Sheba, a married middle class middle aged pottery teacher who has an affair with a 15 year old pupil. It is told by Barbara, a sixty-ish spinster teacher in the same school, in a voice that could easily have been written by Alan Bennett.
It's very different from Lolita. There is no premeditation on the part of the Sheba; instead she succumbs through weakness (not that that's a justification) and excitement. In many ways she is the most childlike character, having married very young and been babied to some extent ever since, first by her husband and more recently by Barbara. Although Steven is a victim, he is also predatory, and Sheba is prey to both him and Barbara (described as a succubus, by Sheba's husband). The fact that Sheba started going out with her husband when he was her lecturer perhaps makes her feel it's not such a big boundary to sleep with Steven.
Although the headline relationship is between Sheba and Steven, it is arguably that of Barbara and Sheba that is more twisted and exploitative. Barbara thinks she is lonely and that Sheba is insensitive to that, but Sheba is at least as lonely in a different way, and not as self-centred. Barbara wheedles her way into Sheba's life, with clear, but implicit Sapphic undertones, and loves the reflected glory of being friends with an attractive family. She subsequently relishes her disgust and revels in the power of secrets. Even when the story breaks in the press, Barbara still gets a vicarious kick out of the scandal and her place in it.
Overall, a fascinating book, with lots to think about.
(My review of Lolita is here: http://www.goodreads.com/review/show/41825911.)