Warner Bros have bought the rights.
I read it a few years ago and didn’t think that much of it - the science explaining the change in Earth’s climate and subsequent regressive evolutionary changes is unconvincing, the characters seem a little too early 1960’s.
But for some reason, it stuck in my memory and I’ve often thought it would make a good film. It reminded me a lot of Heart of Darkness - that may have been Ballard’s intent.
Anyone else think this would make a good/bad movie?
As long as they get Kevin Costner on board, it should be a winner.
It’s been a long time since I read the book, but I remember liking it - aren’t there some bits where they look through the water to the ruined civilisation below? I seem to remember the booking conjuring a feeling of deep, watery loss rather well, but I don’t know how well that would work in a modern film - a single speedboat chase would ruin it.
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I am not sure how well a faithful adaptation would work given all the characters are insane to one degree or another and have quite odd motivations. It does not have a clean conclusion and it all goes rather surreal.
As for seeing the lost world it’s set in a flooded London and at one point a group dam off a flooded section around St. Pauls and drain it as they are trying to mine the city for lost artefacts. There is also quite a bit of the city still poking above the water so it’s not a water world type scenario.
The Kraken Wakes by John Wyndham sort of covers a similar type of flooding and would actually make a much better film.
It must be 20 years or more since I read it, ISTR that I liked but it had a lot of introspection on behalf of the narrator. Like a lot of Ballards stories (e.g. The Terminal Beach or Concrete Island) it has the protagonist searching a barren and/or ravaged territory while also in search of some inner clarity. So yeah, they are all stark raving mad but they want to be mad in a different way :-). It will be difficult to transplant to film.
Then again, they will probably ditch everything but the setting and the names of the characters and insert boat-chases, evil conspiracies and lots of explosions!
I would not be surprised if just plan on taking the climate change part of the story and forgetting most of the rest of it. I would imagine the location is also likely to change. Of course if they do that you wonder why they need the book rights in the first place but then it’s never stopped them in the past with other adaptations. Maybe they will be going with the tag line from the writer that bought you Empire of the sun.
And of course I am sure they will throw in some boat chases and explosions 
I can’t think of a director I would trust with this material.
ETA: Maybe Del Toro