What's it all about, briefly? Senior explores, basically, how having children may be a recipe for fulfillment (sometimes), but it is certainly no shortcut to happiness. She emphatically puts the focus on how parenting affects the parents, which was kind of a welcome change in a book about parenting, to tell you the truth. Early chapters focus on baby- and toddler-raising and issues like sleep deprivation, while later chapters explore the pressures parents are under when their children are in school and are teenagers. Throughout she considers the effect of children on parents' self-perception, work, and relationships (to mention just a few).
Representative quote: "Men and women may, on average, work roughly the same number of hours each day, once all kinds of labor are taken into account. But women, on average, still devote nearly twice as much time to 'family care'--housework, child care, shopping, chauffeuring--as men. So during the weekends, say, when both mothers and fathers are home together, it doesn't look to the mothers like their husbands are evenly sharing the load. It looks like their husbands are doing a lot less. (Indeed, in another analysis of those 1,540 hours of video data, researchers found that a father in a room by himself was the 'person-space configuration observed most frequently.'" (p. 56.)
The Skinny: Worth a read, for the different focus alone. Senior has a pretty nice, streamlined writing style that made this a quick read, and she draws on many interesting sources (scientific studies, personal interviews, books and articles).
Don't have time to read the whole book? You can try Senior's New York Magazine article on the same subject.