The sun has gone mad. The ice has melted, and the continual flooding has covered much of the world with water. Temperatures have risen to the point where humanity has relocated to the Arctic and Antarctic circles just to survive. The result is that cities like London have become lagoons, surrounded by jungles and with only the top floors of the tallest buildings above water.
That's the setting of The Drowned World, and it's by far the best thing about the book. Ballard has quite a way with descriptions here, making his dystopian London vividly real. Yes, it is rather more extreme than most global warming scenarios would call for, but Ballard made it thoroughly believable. And yet it's still, by its very nature, a surreal landscape from a dream, or a nightmare.
The plot and the characters, on the other hand... Not strengths here, no. The plot is rather thin, and deals mostly with the main character, and a few others, mentally regressing in the primordial atmosphere. I'm not sure I really bought into the whole concept, though that may well be a problem more with the fairly weak and shallow characters. Only the villain has had any serious work done in rounding him out, and he is certainly a memorable character. Everybody else, even the main character, are little more than cardboard cutouts. With bonus racism and sexism for good measure. The only female character is nothing more than a prop for the male characters to maneuver around, and there's an uncomfortable air of minstrelsy around the black characters. I could have done without, to say the least.
I had to give some serious thought to my rating for this book. I give very high marks to the setting, world building, and descriptions. But everything else is so underwhelming (and sometimes offensive) that I had to give this two stars.