New worlds! Quirky people! Above all, unsettling ideas! The stories I love best are the ones that ask big questions—the ones that leave me feeling as if someone just stomped in, wearing heavy boots, and rearranged the furniture inside my head.
If you like that feeling too, try Arthur C. Clarke’s sci-fi classics 2001: A Space Odyssey and Childhood's End. Old-fashioned? In fact, 2001 brilliantly confronts us with—and refuses to solve—a terrifying enigma that’s only now about to become real. When we first produce a machine like HAL, which seems to have beliefs and desires all of its own... will it have them? Or just seem to have them? And how will we know? (Philip K. Dick’s Do Androids Dream of Electric Sheep? is another classic on similar themes that also, like 2001, became the basis of a great movie.)
My big fantasy recommendation (new, quirky, and unsettling all at once) is always the first big fantasy novel I read, aged 15 or so. While my friends were falling in love with Tolkein, I preferred reading Mervyn Peake's Gormenghast trilogy. It's not an easy book; the language is dense and odd. And maybe calling it fantasy is odd, too: there’s no magic, not a single orc or talking tree, no wizards or demons. Just "ordinary" human beings (about half of them insane) in a castle. But that castle is a world so rich and colorful (yet so bleak, and weird, and weirdly familiar) that it’s like seeing our world from the viewpoint of a Martian. And it’s hard not to like a book in which the homicidal cook is named Swelter, the mad medic is Dr. Prunesquallor, and you also get one of literature’s great creeps, the ruthless, stop-at-nothing anti-hero, Steerpike.
I always admire good SFF books that —like these— beg to be read by teens and young adults even though they’re not “supposed” to be “YA.” (A pet peeve of mine—in any genre—is the phrase “age appropriate.” I think you should read every good book you can read.) To see what I mean, get your hands on these three: James Gurney’s fantasy adventure picture book Dinotopia(yay: there are many more books in the series). David Almond’s so-called "middle grader," Skellig, which everyone from 10 to 110 should read. And finally, a grown-up, gritty detective novel that’s really something else entirely, China Miéville’s The City & the City (Hint: Beszel and Ul Qoma are such different places. But they’re in the same place.). Is this sci-fi? I’m not sure and I don’t care—it’s brilliant.
Miéville is serious stuff, but I also like my SFF seriously funny. Read anything, anything by Sir Terry Pratchett, but especially The Wee Free Men—preferably aloud, in a bad Glaswegian accent. Also Douglas Adam’s The Hitchhiker’s Guide to the Galaxy series, and Jonathan Stroud’s Bartimaeus trilogy. Oh, yes, and Eoin Colfer’s Artemis Fowl books. A 12-year-old criminal mastermind searching for Irish fairy gold… only, the fairies have unreliable atomic-powered wing-backpacks, and one of them smokes vile-smelling cigars and says “D’Arvit!” all the time—a word the author helpfully explains as a fairy swear-word “too rude to translate.” Hilarious.
I have to finish by recommending Philip Pullman's His Dark Materials, my favorite SFF book by any living author. And especially book two, The Subtle Knife, not just because it's great writing that makes you think about Big Stuff (stomp, clomp: sounds of furniture being rearranged), but because it's such a great metaphor. A magic knife? With which you can cut a gap in this universe? And step through into a different universe? Oh, right... that's what a story is.