Sassen's biggest contribution to the theorization of globalization is her attention to the global city, which she posits as a site of the physical infrastructure that enables the more diffuse projections of the world market. In these cities (like New York, L.A., Tokyo, London, Rio, etc.), high-wage, white-collar workers brush against the low-wage, largely immigrant diasporae that keep the global city running; immigrants form blocs that see a certain degree of enfranchisement and force adjustments in transnational immigration law; and globalization marches on. It's interesting stuff, but it's not new. Sassen's own book on "The Global City" scoops these chapters. And that's pretty much true of the rest of the book.
The two chapters on gender and globalization are much more valuable (and more recent) here, as she starts in on what she calls "the unbundling of sovereignty," the appropriation of political punch from nation-states and the relocation of it into the hands of NGOs and the global market. Unfortunately, while she opens up a great area of inquiry, she doesn't take it very far at all, "since the effort here was not to gain closure but to open up an analytic field." As they stand, these chapters are frustratingly suggestive but ultimately not very thorough or useful. Hopefully she'll revisit the theme later.
The stylistic question is a thorny one; several reviewers have already blasted Sassen for the way she writes. She's certainly not the easiest read, and her incessant neologisms are annoying. ("Operationalizing"? Can we not say, "making operational"?) You can fault her for that. But you can't fault her for writing like a sociologist, and that is largely how she writes. It's dry, there are charts and facts and figures, but the prose is economical and fairly clear (fake words aside!).
By and large, though, this isn't a must-read. If you're really interested, check out her books, "The Global City" and "The Mobility of Labor and Capital." They treat the same subjects, but in more useful detail.
The book is a collection of essays that Sassen has published elsewhere between 1984 and 1997. Except for the introduction, there is no new material here. Furthermore, in many cases the content of one article is reproduced in another article in the book. Rather than reinforcing important arguments, it seems clear that Sassen is trying to get as much mileage possible out of her work. It doesn't work.
The book contains hundreds of endnotes (in many cases they contain the most important information) which should have been incorporated into the text. Furthermore, she offers no conclusion to her analysis and the last chapter itself is quite unsatisfactory.
In short, this book is poorly written, tedious, and unoriginal.