I recently watched "Let Me In." The movie is a love story, and is a perfect inversion of the Twilight movies (sorry didn't read the books). Instead of hokey and sappy, the movie is dark and gritty. Instead of a girl falling for manpire, it is instead a story of boy falling for a vampgirl.
The movie is a metaphor for the obscene, dark-side of love. In the movie, a young boy falls for a young vamp girl. But, in order to maintain his love for vampgirl he must learn to accept her as a monstrous Other. (When he asks if she'll go steady with him, she replies that she can't because she's "not a girl." She's a monster.) Ultimately, to love her, he must sacrifice his duty to the human race, because for her to survive she must kill. After witnessing her murdering people, he decides that she means more to him than human life, and at the end of the movie becomes her accomplice in killing others to keep her alive.
"Love is evil" says Slavoj Zizek. And he is right. Love is loving the Other as Other. Love is accepting the monstrous Otherness that exists in one person, even though we cannot understand it, and can't approach it. Singling that one person out from the entire universe as somehow special, unique, and worthy of praise. This is a violent act. It is a sacrifice. By separating the one, from everyone else, we renounce our duty to the world, and instead commit the evil of valuing one single life, above the lives of everything else. See Derrida in The Gift of Death.
The fact that love is evil, is not a reason to renounce it. On the contrary, love is a break from the entire human order. It is a liberating, but it is also a heavy burden. The act of love elevates the one to the level of the Thing, and is sublime. Love, love, love.