Liz Jensen's much-praised seventh novel, a global-warming thriller set in the near future, has the feel of a lushly filled out film script. Against a backdrop of swirling skies are set some familiar elements, among them an unstable shrink and a demonic child straight out of The Exorcist. It's the sort of film that, despite the promise of its premise, falls apart in the final half-hour.

Gabrielle Fox is a wheelchair-bound art therapist assigned to work with a teenage matricide in a secure unit near Dover. She became a paraplegic after the car accident that killed her lover (and for which she is to blame). She's screwed up and insecure and probably the worst person to delve into the mind of the poisonous and apparently psychic Bethany Krall. Bethany craves ECT, the only thing that seems to alleviate her mental suffering, and after each treatment she rants from the Bible, accurately predicting natural catastrophes. Her obsessive drawings of a diving man turn out to prefigure an earthquake in Rio that dislodges the statue of Christ the Redeemer. Frazer Melville, a passing physicist, falls for what he calls his "sex goddess on wheels", and through Gabrielle becomes embroiled in the Bethany case. As the world simmers, Christian fundamentalism is on the rise; the so-called Faith Wavers are waiting for the Rapture, which the gloating Bethany seems to be foreseeing: the final cataclysm when true believers will be swept up into the heavens. Rejecting the religious interpretation, but fearing the risk of a global disaster is all too real, Frazer and Gabrielle try desperately to warn the experts, all blinkered by their scientific rationalism.

Through the angry, despairing Gabrielle, Jensen convincingly depicts the everyday humiliations of the wheelchair-bound, and much of the writing is powerful  for example, in a phrase like: "[I] brainwash myself into erasing the fickle, freckled physicist from my psyche", where even the silent "p" pulls its weight. Towards the end, however, things take a melodramatic turn and the seriousness and quirkiness that promised so much are jettisoned for flashy effects (tiny humans, vast tidal waves) that are just so much CGI.

Thrillers, alas, do not need to be well-written to succeed. (You could tell The Da Vinci Code was garbage from its very first word. But it was still a success.) So when an entertainment is, at the level of the sentence, up to the mark of respectable literary fiction then the entertainment is all the better  and all the more convincing: good prose is, or can feel like, a guarantor of truth, which makes The Rapture a peculiarly unnerving book, and all the more timely for coming in the wake of the failed negotiations of Copenhagen.

We are in the near future: far enough away for the London Olympics to be over, and for there to be a birdshit-spattered statue of Margaret Thatcher in a smallish coastal town (actually, a detail like that is dystopia enough for me); but near enough for everything to be recognisable to the point of complete familiarity. Without the signifiers of the statue and the Olympic stadium, Jensen might as well be describing our own world  with the differences that the world has already got a lot hotter  in the summer, everyone ventures out in sunglasses; and there has been a huge growth of fundamental Christian sects, particularly the ones with an apocalyptic bent.

We meet, in an institution for psychotic youngsters, one Bethany Krall, who had, a couple of years previously, stabbed her mother to death with a screwdriver. Her father, a preacher in one of the sects, has disowned her. Bethany's art therapist, Gabrielle, who narrates the book, becomes alarmed by Bethany's ability not only to know exactly what is going on in people's heads (which she exploits with malevolence and relish), but to foresee, with complete accuracy, forthcoming natural disasters. Which are, as is the convention of apocalyptic fiction, increasingly common. A hurricane in Rio, a volcano in Samoa, an earthquake in Istanbul . . . you know the drill. But then Bethany starts to mention another disaster, much, much bigger than all the rest: "It's something new. No one's seen it before. It starts in one place and it spreads everywhere. Too fast for anyone to do anything about it."

To be honest, my initial exposure to the book when it first came out was, then, accompanied by a certain sense of ho-humness; after all, we have been reading about screwed-up weather at least since Martin Amis wrote London Fields, and few, if any, have improved on his descriptions of ruined skies. But The Rapture managed to get right under my skin, and I have not even been put off by the Specsavers TV Book Club "Best Read" sticker on the front, or the news that this is probably going to be made into a film (which I hope doesn't take too long to get made, given the short time we have left on earth according to this book). On the contrary, I find it rather heartening, for if there was ever a book that should be read by lots of people then this is it.

Its success lies in the way it manages to make complete global disaster sound entirely plausible. On a reread, I have begun to think those little thoughts which usually spoil a book for me first time round  such as: isn't the love story a little trite? Isn't the pacing of the book a little formulaic? Isn't the whole premise frankly preposterous? But I am not thinking those thoughts very much because I am susceptible to A Good Yarn and I didn't think them at all first time round. Instead all I was thinking was: what's going to happen next? And: we're doomed. That is, apart from such responses demanded of the critical eye: such as an appreciation of Jensen's ear for dialogue and feel for character  Bethany and Gabrielle are particularly well-drawn; Bethany could have been most tiresome, except that her speeches crackle sulphurously off the page.

But the thing is that Jensen, with her stylistic skills, could have written a perfectly gripping novel without any supernatural or outlandish element at all. She has, indeed, done so in the past, and it would be a pity if her recognised talents were to be belittled by the fact that she has written a page-turner, however superior it may be. And it really is superior. Prepare to be horribly spooked.