Though some of their social analysis is less than fully thought out--surely e-mail isn't a truly unique form of communication, as they suggest--the work as a whole is strong and merits attention. Science, it turns out, does have much to say about our messy feelings and relationships. While much of it could be filed under "common sense," it's nice to know that common sense is replicable. Hard-science types will probably be exasperated with the constant shifts between data and appeals to emotional truths, but the rest of us will see in A General Theory of Love a new synthesis of research and poetry. --Rob Lightner