Neal Stephenson likes writing smart, capable characters who aren't interested in spending time languishing in self-doubt or worrying about what makes themselves tick. They're not often the military or cultural or political movers and shakers in the worlds he creates, but they're the motivational forces in their own lives. To support the confident, forward-thinking worldviews of his characters, Stephenson's style is witty and conversational, never opting for dry exposition when a winking exaggeration would be funnier. Sometimes his characters, generally thin to be begin with, become lost under all that cleverness, but The Diamond Age is so much fun to read that it's hard to blame him for that. It's an engaging style in which to tell tales of characters who are leading interesting lives, both in a biographical sense and in that of the traditional Chinese curse.
That these same interesting people are necessary for the continued progress of society is the central theme of the novel. The book's setting underscores that by setting up different "phyles," each in conflict with the others as competing social organisms. These tribes are based around ideology and culture rather than birthright and ethnicity, thus allowing the book to sidestep any worries about racial politics in favor of opening a debate about whether or not some cultures are inherently better, or at least inherently better suited for survival, than others. The notion of government has been replaced by these tribes, but since the tribes largely serve the same purposes as governments, this mostly just means that cultural institutions are bound together by ideology rather than geography.
The plot is bifurcated, following the lives of a nanotech engineer who builds the quasi-sentient book of the novel's subtitle and an impoverished young girl who accidentally ends up with a copy of said book. That book is designed to create the previously-mentioned interesting people in a world that its commissioner fears is becoming too staid as a result of the ubiquity of nanotechnology. (Given all the goings-on in the background, that fear seems completely unfounded, but it does serve as a means of egress from one social stratum to another, allowing us to get a view of many of the disparate phyles which populate the setting.) Stephenson is a creator of intensely memorable scenes, but the connective tissue between those scenes is often atrophied and sometimes entirely absent. As a result, individual episodes have their own internal rise and fall, but the overall plot wanders quite a bit rather than following any internal structure. Those meanderings are often quizzical in their intent, as the book has a tendency to cut away at strange times and peek in on other plotlines which possess much less urgency, but they're also quite light-footed and don't dwell on any one focus for long, with the result that their rapid-fire progression makes up for the lack of any coherent overall arc.
By keeping the pacing brisk and giving its characters a lot to do, The Diamond Age distracts us from the fact that there's not a lot going on inside the heads of these people. Major revelations and psychological reconfigurations are given no more narrative attention than mundane details, and major shifts in character identity are treated almost summarily. It's obvious that Stephenson simply isn't interested in spending a lot of time having his characters agonize over their traumas and triumphs, and rather than force himself to write about a topic which he doesn't care about, he gives his readers enough information for them to at least understand his characters, if not actually empathize with what they're experiencing. How closely your own interests coincide with Stephenson's will dictate whether you think this approach to characterization is lazy or graceful.
The reactionary gender politics the characters display are a bit rough to read, though at least they're not based on any kind of statement about the innate inferiority of women but rather on the mores of the two dominant cultures we spend time with. It is a bit puzzling as to why these cultures were chosen by their progenitors as the ones which they should hearken back to, given that both of them historically imploded under the weight of the very virtues that their neo-iterative versions emulate. It's not much of an imaginative stretch to envision that a group of people would idolize an earlier culture so strongly as to ignore its flaws or assume that they won't fall prey to them, though, so this is a completely forgivable bit of worldbuilding.
The Diamond Age foregrounds pervasive nanotech as a way to examine what the basis of value is in a culture in which material goods no longer have any commercial worth. Though nanotech has made the production of standardized goods into a nearly free proposition, it hasn't effected enough of a singularity event to have abolished economics completely, so there are still socioeconomic strata in and outside of the various phyles. What has become more valuable than diamonds is the ability to innovate, an aptitude tied directly to the capacity for critical thought. The novel posits through its characters that critical thinking is earned via hard experience, particularly traumatic experience. This theme doesn't ever get in the way of the story, but rather runs throughout it as a means of both relaying setting information and relating the media-saturated world of the novel to our own. That tendency is reflected in the book's other higher-order concerns as well: though a lot of high-octane ideas get tossed around, none of them are allowed to overwhelm the sheer entertainment value of reading the text for its own sake.
