SOMETIMES PEOPLE who are really good at what they do decide to make things more difficult for themselves. Evel Knievel added a fourteenth bus. David Foster Wallace endeavored to make tax accounting lively. And now, in his new young adult novel Railsea, China Miéville, perhaps the most exciting speculative fiction writer working today, has decided to set Moby Dick on land and (why not?) on trains.

That audacious a premise is not a huge surprise from Miéville, a writer who has famously set himself the task of writing a novel in every genre, and who even then isn't content until he's set a believability-defying challenge. (Can two cities occupy the same space and never touch? See The City & the City. Can a language be built only on direct referents? See Embassytown.) But the danger of too elaborate a premise is the possibility of jumping the shark — or, in this case, literally losing the shark. How can a train bound to tracks hunt a quarry that is not? What if the "whale" decides to turn left? Wouldn't a car become a better option?

That Railsea satisfactorily answers these questions and wriggles out of many more self-imposed knots are among its chief charms. I'll avoid spoilers, since part of the fun of this kind of speculative fiction is its slow, sneaking exposition. The mystery is implausibility; the reveal is how it all makes sense. But a few hints to get your bearings: The whales are actually giant moles, or "moldywarpes"; the railroad tracks are an enormous tangle of switchboards, or the "railsea"; and there are plausible historical reasons for the existence of both of these things, including ecological disaster and out-of-control public-works spending.

All of this elaborate scaffolding lets Miéville build a deliciously clever homage to Moby Dick. The opening molehunt is a stylistic romp:

The moldywarpe reared, the moldywarpe roared. The spear juddered. The harpoon rope whip-unwound as the animal thrashed, blood on the soil. Rails buckled & the cart careered, tugged behind the animal. Quick — they knotted a soil-anchor to the  line & threw it overboard....

Until at last in a lagoon of stony steppe, a dirt space in the infinite rails, it stopped. It quivered, then settled. When next the greedy railgulls landed on the furred knoll of its body, it did not dislodge them.

... & no illustrations; no flatographs; no salvaged thriddies, paintings, saltprints or liquid-crystal renditions; & certainly not the arse-achingly dull molers' reminiscenses Sham had heard too many times could have prepared him for what extraordinarily stinking work followed.

The risks Miéville takes — the neologisms, the ampersands — are justified by the meaty gorgeousness of the passage. Each also assumes a deeper meaning later in the book: the ampersands have their purpose, and "salvaged thriddies" isn't a throwaway phrase. But most of all, they work as a loving parody of Melville. Railsea is irreverent, and that's the fun of it. We learn early that n...