But yeah, Stephenson isn't the author to start non-sci fans on (though Vonnegut fans might love Cryptonomicon and spot an influence or two). Atwood's Oryx and Crake is probably my answer to that, since it's classic near future sci fi disguised as literature. The first book is all about near future society and the implications of plausible tech, she just writes about the people in it and doesn't waste words describing the details of stuff they wouldn't know or how it actually works. And the subsequent books are cliche-trope heavy dystopic sci-fi and still probably doesn't feel that way to people who tend to avoid that stuff.
Cryptonomicon is one of my favorite books, but I also once described it to a friend as "one very long dick joke".
I really like Diamond Age, it's probably one of my favourite books, and if that was his only novel which did it I'd say well, fair enough it sort of makes sense in context - but it happens over and over, so that's not great. It's in the same category as Fridging in comics. Twice is coincidence, three times is lazy writing.
I still enjoy his writing, and generally think he isn't a bad writer, but also...
Absolutely not Cryptonomicon unless you're sure they're libertarian and male. I reread this recently and I think it aged very poorly for women and liberals because what was once a quirky set of characters in the modern part of the story are now a widespread and polarizing demographic today (our free thinking hero has to deal with some very exaggerated wokeness, and spends a few pages explaining that women aren't as obsessed with tech because they're so good at everything else).
This is not the author to start people who aren't into sci-fi on though. I really love some of his books but I think anyone who can get through one of them is probably already a sci-fi fan. There's more immediately fun books that people can get hooked on like Vinge and Brin or more literary and less tech-describing stuff like Ursula le Guin that appeal to wider audiences and from which they can look for other books with the same themes