Although there are many kinds of love, erotic love has been celebrated in art and poetry as life's most rewarding and exalting experience, worth living and dying for and bringing out the best in ourselves. And yet it has excused, and even been thought to justify, the most reprehensible crimes. Why should this be? This Very Short Introduction explores this and other puzzling questions. Do we love someone for their virtue, their beauty, or their moral or other qualities? Are love's characteristic desires altruistic or selfish? Are there duties of love? What do the sciences - neuroscience, evolutionary and social psychology, and anthropology - tell us about love? Many of the answers we give to such questions are determined not so much by the facts of human nature as by the ideology of love. Ronald de Sousa considers some of the many paradoxes raised by love, looking at the different kinds of love - affections, affiliation, philia, storage, agape, but focusses on eros, or romantic love. He considers whether our conventional beliefs about love and sex are deeply irrational and argues that alternative conceptions of love and sex, although hard to formulate and live by, may be worth striving for.