The book centers on Nell, a four- or five-year-old girl with a thuggish yet protective older brother, Harv (short for Harvard, awesome). Through a series of events, Nell becomes the owner of the Young Lady's Illustrated Primer, a cutting-edge "book" that adapts itself to one user, and teaches that user how to survive/thrive in her environment. Other people want the Primer, too, namely: John Percival Hackworth, the engineer who created it; Lord Alexander Chung-Sik Finkle-McGraw, the aristocrat who commissioned the Primer's creation; and Dr. X, a mysterious backroom dealer from the Celestial Kingdom (Chinaaaaa!). All three men want the Primer for one of their own: Hackworth for his daughter, Finkle-McGraw for his granddaughter, and Dr. X for, well, I shan't spoil it, but oh my, what a twist. Meanwhile, the ractor (interactive actor) Miranda, who does voice work for the Primer, becomes interested in meeting the girl who is clearly not living in a safe home environment.
Nell's "schooling" via the Primer, and the hunt for said item, takes place in a post-scarcity world divided by cultures rather than nations. In The Diamond Age, values and ideas matter more than ancestry. The New Atlantans embrace Victorian principles; the Celestial Kingdom follows Confucius; there's a phyle solely dedicated to handicrafts; and so on. Meanwhile, Nell is a thete -- people without tribes, and who get the lowest jobs. The cultures, or phyles, remain at harmony with each other through the Common Economic Protocol, and they deal with intruders through nanotech warfare. All material goods are created through matter compilers, which get their molecules and energy from the Feed.
To use a geological analogy -- while Nell's relationship with her Primer lies at the core of the story, and the various searches for it represent the mantle, the crust turns out to be one phyle's attempt to hack the Feed, to replace it with something more culturally appropriate. All the layers of the story present questions. For instance, what is the best way to educate a child so he/she rejects convention and stagnation? How does circumstance coincide with formal learning to foster personal and intellectual growth? How do insular societies succeed? What are the limits to drive and motivation? How far can artificial intelligence go? Why am I hungry again?
But enough about that. Stephenson wrote a damn good story, and I highly recommend that all sci-fi fans, or open-minded awesome people, pick up a copy of The Diamond Age. It takes standard story elements -- character development, conflict, etc -- and threads them with lines of sheer genius. Gold, I tell you! Pure gold! Or should I say -- pure diamond?*
*Although technically, advances in nanotech would have made it easy to reassemble carbon atoms into diamond structures, rendering the once-precious metal not-so-special. = NERD ALERT! ...oops, too late?