We started this essay with a basic question: if you wanted to recommend a classic Science Fiction book to a modern reader, what would it be?

Conventions change with every new generation of readers, and it takes a special sort of story to remain enthralling and relevant in spite of the passage of time. Science Fiction has an extra burden: since much SF predicts what the world will look like in the future, a story may diminish in appeal if those predictions turn out to be too far off the mark when the 'future' actually arrives.

So here's the uncomfortable realization we came to as SF fans from the older generation (How old, you ask? Mind your own business). Some of our beloved favorites just haven't aged all that well. Even when we're talking about the works of legendary authors, we find many classics have lost some of their luster over the years.

Maybe an author's social prejudices are a bit too reflective of his time to appeal to as many readers today. Maybe an idea that was once revolutionary ("What would an alien intelligence be like?") has been explored so thoroughly it's lost some novelty. Or maybe the author's brilliant speculative gifts didn't translate into an ability to write compelling, believable characters and riveting plots.

Whatever the reason, we had to admit it: we can't just take any of our cherished paperbacks off the shelf and hope a younger reader will love it as much as we did.

But there are still plenty that stand the test of time.

We've picked an arbitrary cut-off date of 1990, and put together a list of just a few classics we think are just as powerful today as they were when they first came off the press:

• The Hitchhiker's Guide to the Galaxy by Douglas Adams When it comes to science fiction humor, nobody did it better. What's extraordinary about the Hitchhiker's books (and Adams' Dirk Gently books as well) is the way Adams could use things like improbability drives, depressed robots, and useful ear-fish to reveal deeply relevant insights about human nature, our relationship with technology, and the mind-boggling strangeness of life in an infinite universe. Skip the 2005 movie adaptation, but the Hitchhiker's books (and BBC radio show) are just as brilliant today as they ever were.

• The Left Hand of Darkness by Ursula K. Le Guin Some books actually get more relevant as time goes by. As the social discussion about the nature of gender identity ramps up, Le Guin's masterpiece published in 1969 shows how a truly visionary thinker can anticipate the steps we will take in human evolution. At the core of The Left Hand of Darkness is a story of loyalty, betrayal, and human connection beyond external appearances--themes that will never go out of style.

• 1984 by George Orwell Probably the most famous dystopian novel ever written--with good reason. Today Winston Smith's travails seem more relevant than ever. Everywhere he goes there's a screen spouting propaganda. 'Big Brother' is always watching. And the facts are slippery concepts, constantly being overwritten. All this is terrifying enough but ultimately the government wants to control what people think. Even though its titular date is long past, 1984 is still a scary cautionary tale for our time. Makes you wonder if Orwell had a time machine...

• Neuromancer by William Gibson Gibson was the first breakthrough pioneer of "cyberpunk"--a brash new kind of SF that rejected utopian notions of progress and took an uncompromising look at technology's power to redefine humanity. Published in 1984, Neuromancer still feels fresh and vibrantly alive. Even though current technology has made some parts of the book archaic (Gibson didn't predict cell phones, for instance), the unique and Gibson's razor-sharp writing still have the power to captivate.

• Startide Rising by David Brin It's dolphins in space. A crew of intelligent, "uplifted" dolphins pilot their first starship into a big, dangerous galaxy. Brin's Uplift Universe books are good reads in general, with engaging characters, big ideas, and seat-of-your-pants drama, but Startide Rising is the stand-out book in the series. Why? Because it's dolphins in space. And they even speak in haiku.

There are plenty more timeless SF tales, of course. Why not head over to the blog and tell us what your favorite is?