Risk becomes a dirty word to many genre writers once they develop a rabid fan base. As long as the cash registers keep ringing and the fans are happy, why take chances? Indeed, the most rabid fans tend to insist that their favorite writers not only stick to their chosen genre but produce the same book over and over again. That’s why we keep getting robotic, risk-averse re-writers like the late Robert B. Parker.

Given all that, China Mieville is to be loudly applauded for his new novel, Embassytown. For starters, it’s a work of pure science fiction, which is to say it’s a departure from his seven previous fantasy novels, books of ravishing imagination that have won him a cult following and critical praise, including a career retrospective here last year. Instead of doing the safe thing and revisiting his imaginary world of Bas-Lag or his reconfigured city of London, Mieville now takes us to his titular “city of contradictions on the outskirts of the universe.”

Embassytown’s human inhabitants live under a breathable dome, surrounded by a city full of indigenous Hosts, or Ariekei, winged, chitinous creatures with antlers of eyes. The Hosts speak Language. The only humans capable of understanding and speaking Language are the Ambassadors, highly trained twins, or doppels, with linked minds who are capable of making paired sounds simultaneously. The Hosts, who are incapable of lying, bridle against their innate literalness; that is, they yearn to be able to lie. Their yearning is summed up in the novel’s epigraph from Walter Benjamin: “The word must communicate something (other than itself).”

A girl named Avice is recruited to become a simile. She’s taken to an abandoned restaurant, where a group of Hosts perform a mysterious ritual that enables them to call her a girl who ate what was given her. This gives Avice exalted status, and she grows up to become an immerser, a sort of intergalactic merchant marine who surfs the far reaches of space. “The immer was and is full of renegades and refugees,” she reports after returning to Embassytown. “I had transported many things to most places; jewellery; immer-immersible livestock; payloads of organic garbage to a trash planet-state run by pirates.”

The Hosts and humans co-exist in an uneasy peace that is disrupted when a new Ambassador named EzRa arrives in Embassytown. When EzRa speaks Language, the Hosts become addicted, which will lead to a siege of Embassytown, and eventually to total war between humans and Hosts.

Mieville’s phantasmagorical imagination is alive and well. Architecture in the city is organic, changing shapes, producing antibodies; purses grow on bio-rigged trees; there are flying machines called “corvids,” and computers in segmented bodies called “automs.” There are many verbal delights, sentences like this one after Avice meets her future husband: “We were in a bad hotel on the outskirts of Pellucias, a small city popular with tourists because of the gorgeous magmafalls it straddles.”

The novel, for all its inventiveness and linguistic verve, is not flawless. In the early chapters we can see Mieville straining to lay the building blocks of Embassytown, the surrounding city and the farmland that brushes against a “gently toxic sea.” It’s obvious he’s feeling his way, sometimes groping. The book is one-third gone before the gears of the story mesh. The wait is too long, and nearly disastrous.

But Mieville salvages the novel by giving us a rich story that is, first and last, about language – its power to bring humans and aliens together, and its power, when misused, to turn them into mortal enemies. Once EzRa begins to work his dark magic with Language, the novel takes off, moving smartly to a climax that is built not around a rote battle scene, but on the healing power of a new language. It’s a bewitching performance by a writer who deserves praise for daring to do something rare among writers of his stature: He’s willing to walk the high wire without a net.