Conti enumerates all of Google's (often fantastic) services, describes how compelling they are, and then notes what information you disclose when you use them -- even when you only use them inadvertently (say, when you send email to someone with a Gmail account, or when you load a bookmarked Gmap that's been sent to a group of logged-in Google users, thus tying yourself to those users as part of the same group).
In slow, methodical steps, Conti builds his case: our complacency, Google's capacity for building compelling services, and the inadequacy of our browsers and other tools in alerting us to potential information disclosure have created a situation where Google ends up in possession of an alarming amount of information about us, our beliefs, our movements, our finances, our health, our employment and our social circles.
Conti's explanations are extremely accessible, even when discussing difficult and counter-intuitive subjects like cross-site scripting and cookies. Likewise accessible are his concrete recommendations for staunching the flow of personal information from your computer into Google's records. Finally, Conti does a great job of explaining why people who "have nothing to hide" might still want to keep their information to themselves (the approximate dimensions and characteristics of the body under your clothes aren't a secret -- but you still don't walk around naked in public and you'd resent it if someone forced you to. Private and secret aren't the same thing).
I've given the subject of privacy and Internet use a lot of thought, but even so, Conti's book opened my eyes to potential risks I'd never considered. I'd recommend this to anyone who's worried about what's happening to our ability to control the aggregation of our personal data.
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.