I am puzzled by one of the negative reviews of this book: Armstrong does deal with jealousy, approaching it from an evolutionary psychological perspective; he does cross reference; his bibliography includes some of the most notable books written on love; and if he refers to 'females', at least he is consistent by referring to 'males' too. True, he doesn't cite texts on love written by women, and that is a shortcoming, but this lack certainly does not lead to a one-sidedness in his discussion of love. You may not be satisfied with what he says about all or some of these things, but at least do him the small honour of giving an accurate account of what the book contains.
I liked this book. I thought Armstrong did a good job of showing how our idea of love has evolved over the millennia, how revolutionary ideas such as evolution, Marxism and psychoanalysis have left indelible marks on our idea of what love is, enriching the concept while also making it increasingly more complex. All of this is done in a comprehensible language, with a logical structure, and easily manageable and sensibly divided chapters.
Armstrong's argument seems to be that there is no essence of love, and that to go in search of a hard and fast definition is doomed from the start and based on an error of thinking. Love is not any one thing, but a host of related things which are neither identical with each other nor legitimately reducible to something held in common. He shows the many aspects of love: friendly, parental, childish, long-term, passionate, unrequited, and so on. You are left ultimately with an impression of the complexity of the notion and the futility of the attempt to reduce it to one simple thing, an endeavour which the question 'What is love?' all too irresistibly invites.