The Three Stigmata of Palmer Eldritch, because it made me laugh and shiver at the same time.
1) Holy communion sold as a drug to keep the poor bastards drafted to farm the semi-desert of Mars from killing themselves. One of the richest man in the solar system sells the (addictive of course) drug, Can-D, that provides the experience. The foci of this communion are Perky Pat and her boyfriend living the 1950s white suburban dream, so there's a highly profitable sideline in miniature clothes, cars and household appliances to flesh out the dream.
2) The title character offers a substitute drug, Chew-Z, that's non-addictive, but the side effect is that Eldritch is permanently a part of your personal universe. Filmed, more or less, as "Wild Palms."
Insane and plausible at the same time.
Shockwave Rider (1974), John Brunner. A lot of it came true, but you can say that about a lot of imaginative SF. But the story also leads you to the crux of the central character's motivation. This inspired a lot of geeks, none more so than Robert T Morris Jr. who, in 1988, wrote a worm that disabled 6000 hosts on the then much-smaller internet.
The Diamond Age, which is Alice in Wonderland within which Alice grows up, with the help of those who built the Wonderland. Also, it's got great gobs of social commentary, which I love.
Frankenstein, because it nails us for pretending to be gods when we really need to be just good parents. Whether creating life the usual way or innovatively, out of a test tube, from ones and zeroes, or, what the hell, body parts Abbie Normal's brain and a bolt of lightning, you still have to change its diapers annd eventually see that it gets into a good school. It'll quickly figure out that we're not its gods, and less hangs on the question than we want to admit. If Monsanto or the Raelians clone a baby its future becomes a matter for social workers, not patent lawyers.
The science of Frankenstein wasn't bad for the time. Lack of characterization is more than outweighed by the enduring moral, which we show no signs of learning anytime soon.