Pop keeps telling me that he tried to recommend Neal Stephenson books for my nephew's voracious eyes, but that he 1) spelled the author's name wrong, and 2) has some concern over sexual content which you may or may not have pooh-poohed.
His name is spelled as above. He's an awesome writer. I would enthusiastically recommend any of his novels, though have no idea of age propriety -- I suspect when you have a child reading way beyond his "age appropriate reading level" that some control over content may be ceded or lost. He has written a bunch of novels, of varying essential seriousness; each of them contains fantastic technical explanations (of data processing, or packet switching, epistemology, etc) and really creative visualizations of either his future societies/technologies, or the zeitgeist of the past.
Chronologically, I don't think I've read The Big U. And would probably skip Zodiac (though it has its moments).
Snowcrash is "cyberpunk" sci-fi, about a hacker and a skateboard courier trying to save the world. One poignant sex scene, resolving a plot crisis and illustrating yet another clever future technological artifact for the protection of women. The first half of this is like a comic book; the second half gets bogged down in theological speculation, retaining some pretty good action scenes, and then ends suddenly. I think the satisfactory ending qua resolution-of-established-plot-arcs requires careful following of the theological speculation, which is sort of out of resonance with the vibe of the rest of the book.
The Diamond Age is set further in a nanotechnological future. Very interesting distributed electronics and ubiquitous computing. I don't recall any sex, but one character did get involved with a cult at one point, and might have been being ravaged (among other things) before he lost track of his identity. This is a pretty serious book despite its densely packed playfulness. Ending is sudden and unsatisfying.
Cryptonomicon is probably the best place to start. It is both a WWII story about the development of cryptanalysis and invention of the automated digital computer, and a story about some silicon valley entrepreneurs starting businesses and trying to establish a paranational "data haven" on a pacific island. It is several types of stories: WWII action, war and industrial espionage, i guess broadly, historical adventure with some silicon valley of the '90s hype tacked on. There are sexual references, only one of which is fairly explicit, but that one is buried in a really dry discussion of Gomer Balstrod furniture and a technique of electronic eavesdropping called "EM Phreaking," so could be missed. Come to think of it, though, there is a pretty detailed, and fantastically interesting, discussion of one cryptanalyst's productivity over time plotted against periodic "manual" and otherwise "override" operations.
The "Baroque" Cycle is three long books (Quicksilver, The Confusion, and System of the World), broadly about the invention of calculus, the protestant revolution(s) in the UK, the invention of capital markets in Amsterdam, alchemy, and, in general, the atmosphere of Europe around American colonial times. Interestingly, several of the characters in these books are ancestors of the protagonists of Cryptonomicon (even Balstrod). There is sex in these, some of it vague and weird. Pop remembers a torrid scene in book III that I don't. A lot of other strange proclivities, not necessarily erotic, are described too.
He has a new book out, not sure what it's called, something like "Altheia" but with another syllable or two. It's real parallel universe sci fi, I'm told, but don't know yet. It's sure to be stimulating.
(Anathem is about the, for want of a better word, parallel world "Arbre" where intellectuals have, for thousands of years, lived under cloistered monastic rule of a sort, on the eve of their first contact with space-traveling entities from other, for want of a better word, parallel worlds, and a lot of lengthy discussion as to what might be better words (or a better paradigm) to use in attempting to contemplate such situations. It is a masterpiece. - ed.)I daresay, if he's reading that typical pulp adventure novel with its one predictable obligatory sex scene probably irrelevant to the plot and reinforcing a dominator/piece-of-meat mode of gender roles and sexuality, the frank and thoughtful discussion of their motives offered occasionally by Stephenson might be . . . a nice contrast. Most of his stuff isn't glamorized, as I tend to recall it is in the above specified mode (if you can call that glamor; i think you can, though, maybe wryly) of detective/mystery/adventure pulps.
Most of these books have moments of fantastic violence. The hacker in Snowcrash ("Hiro Protagonist") uses samurai swords, and his colleagues use more terrible weapons more frequently; some judicial systems in the Diamond Age use nanotech implantable explosives to enforce sentences; Bobby Shaftoe is a really tough marine who participates in some grisly horrors and psyops in Cryptonomicon; the Royal Society dissects living animals, people are mutilated, blown up; Cromwell's head is left to rot for 20 years; some war and vagabondery involving guns and swords in the Baroque Trilogy.
(And Anathem routinely contemplates megadeath, historically and through threatened use of "the world burner" and deployment of banned "everything killers" within the course of the narrative - ed.)