We're told that all fiction, and especially commercial fiction, must have characters and plots. Is this really true? In the last couple years I've noticed a number of outstanding science fiction stories which are really expositions of ideas, with no pro/antagonist conflict to resolve, no clear narrative current; it's a lot like reading non-fiction, and it's often excellent. What's more, I find that imagination can fly more freely in this style of fiction because the writer can keep piling on ideas and innovations one after another, and isn't that why we're reading speculative fiction, for ideas? If you disagree and you like Borges, then you have some explaining to do. Even when he does have characters, they often function only to introduce a puzzle at the beginning of the piece, and then exeunt as the ideas take center stage. (Not everyone appreciates fictions of ideas, or they miss the boat entirely; more here in the context of criticism of Mieville's Embassytown.)
Granted, it may be good advice for aspiring writers to master the more traditional and likely easier structures of modernist, character-and-plot driven narrative fiction - but there are subgenres of science fiction which are clearly about ideas, and they suffer for their conservative insistence on crowbarring characters into the story. This is hard science fiction's cardinal sin; how many stories have you read that seems grudgingly salted with characters whose dialogue is basically to read aloud the technical manual for some interesting concept the writer is considering?
Since I greatly enjoyed Ken Liu's Hugo-nominated story, I've been devouring everything by him I can find, and his "The Bookmaking Habits of Select Species" is an excellent example of this expository style. The story delivers exactly what the title promises: a description of how various aliens write and regard books, and it's nothing short of addicting. Rarely have I been so sorry when a story ends. Liu also seems to anticipate his reader's thoughts and objections, and you feel as though you're in a dialogue with him as you read. (He's a practicing attorney; this may not be a coincidence.) Kij Johnson (whose Spar I loved) is nominated for the Hugo for Mantis Wives, which is more clearly allegorical, but getting to what that allegory places more demands on the reader.
The writer I've seen doing this most explicitly - and discussing it explicitly in inteviews - is my favorite new writer, Yoon Ha Lee; another piece linked here.