Triumph of the City by urban economist Edward Glaeser (Macmillan, 2011) is highly recommended. Although the son of an architect, he is not a fan of solving cities' problems by building things: 'help poor people, not poor places' is a recurring theme of the book. A perceptive outsider's take on one's own field is often refreshing, and while this stat-fuelled account of why cities are the key to progress, growth, enlightenment etc. concerns itself for the most part with people and economic activity rather than buildings and infrastructure, the parts of his arguments that relate to the built environment are filled with useful iconoclastic observations of the kind that fall flat when one tries them oneself but command attention when delivered by a Harvard prof.
For example, he suggests that if conservationists were a bit more logical (a bit more like economists, I think he means) they would argue for buildings not in conservation areas (I'm translating from American into English here) to be as tall as possible, not as short as possible, to reduce future pressure to redevelop the things they are trying to protect. Conservationism is fingered as having the direct effect of keeping property prices high and excluding the less well off, in respect of jobs as well as homes. NIMBYs are revealed as the unthinking slaves of the combined effects of two well-understood psychological syndromes that apply to reactions to change generally: the status quo bias (over-attachment to the present state of affairs) and impact bias (over-estimation of the impact that a negative shock will have on one's happiness).
Glaeser is for density and against sprawl, while being honest enough to explain why he and his family moved from downtown to the suburbs (schools etc., just like London). He hopes that India and China will avoid the perils of new cities growing at low rather than high densities as they mature, and speculates that 'in the long run, the twentieth century fling with suburban living will look, just like the brief age of the industrial city, more like an aberration than a trend'.
The title of the book might suggest you are in for some urban boosterism, but Glaeser is a lot more thoughtful than that, and he provides a powerful ethical as well as an economic basis for promoting densification.