This is Your Brain on Love
Researcher Helen Fisher argues that the feeling of romantic love creates changes in the brain that are similar to those undergone by someone with narcotic addiction.
This does seem to describe very well the kind of obsession that many people talk about with eros.
One hesitation I have about her discussion is her description of romantic love as a feeling, distinct from sexual attraction, that singles out one person as worthy of exclusive attention for the purpose of mating. This seems to essentialize heterosexual monogamy into biology.