Bruce Sterling is a bright guy, a perceptive futurist, and the author of 10 novels — three of them New York Times Notable Books of the Year. Along with William Gibson and Neal Stephenson, he’s one of the three most important science-fiction writers around. He has won two Hugo Awards for short fiction.

Which is amazing, given the grave sins against prose fiction in his latest novel, “The Caryatids” (Ballantine, $25).

Don’t get me wrong, the book bristles with technological ideas and social insight, features fascinating if not altogether credible characters, and even manages a certain narrative momentum.

But providing a modicum of vision and entertainment value is not the same thing as writing a good novel.

The title characters are seven cloned sisters, their “mother” a mad Balkan war criminal. The surviving sisters — Vera, Radmila, Sonja and Bizerka — may or may not have the gifts needed to save the world from pending ecological calamity.

Bizerka being a nutbag terrorist, Sterling focuses on the other three, a clever strategy that uses each as an entry into the life, strife, business and politics of the world’s three powers in 2060. The Dispensation, centered in Los Angeles, aims to turn a profit with popular entertainment. The Acquis, a “bright green” European collective, works to rehab nature through the application of radical technology. China, the last nation, survives by sacrificing half its citizens.

Best of all, Sterling has written an optimistic novel, showing it may be possible for humanity to survive dire challenges.

Too bad “The Caryatids” reads as if Sterling typed it while wearing boxing gloves. The prose is not only inelegant, but at times rife with the kind of missteps you would expect from a first-year creative writing student.

For starters, Sterling often tells rather than shows his story. In the space of 1 1/2 pages, he tells us three times that a certain male character is “ugly.” What does ugly even mean? As a storytelling word, it’s as vacuous as “beautiful.”

“Vera analyzed her boss’s ugly face.” Ugly how? Swollen nose? Bad skin? Lazy eye? Nope, just “ugly.”

When Sterling does move aside the exposition for actual scenes, the characters do not behave, or — especially — speak like real people. Dialogue tends toward speechifying, often in the tones of a position paper. Or it reads like something out of a second-rate telenovela: “Well, you can’t break me, you little whore! You never could, you never can, and you never will.” Bwa-ha-ha-ha!

Sci-fi aficionados, thrilling to Sterling’s mastery of future technological and social possibilities, might scoff at this kind of criticism. But his sins against basic principles of narrative prose exist right there on the page. Just because sci-fi is a genre doesn’t mean we should grade it on a curve.