At one point in this novel a character expresses the view, "I'm not sure if we've been invaded or if they're just spraying the garden." Aliens have seeded the Earth with giant Plants that tend to eliminate all other plants by out-competing them for basic resources such as water and sunlight. Machines are systematically wiping out not merely humans, but all mammals. A band of survivors in the former USA struggle against Plants, aliens and - themselves. Despite the likely imminent extinction of the species, people still can't stop themselves from getting involved in destructive power politics and personal rivalries. It feels depressingly realistic.
The story is interesting and the bleak but realistic idea that if aliens with interstellar travel technology turned up here and didn't like us we wouldn't stand an - Earthly? - chance is in stark contrast to the much more commonplace scenario that the aliens will be defeated by their own hubris e.g. The War of the Worlds or humanity's intrinsic superior adaptability and inventiveness e.g. nigh-on every alien invader story from the 1950s on. But that isn't really what this book is about. It is in fact about spraying the garden - with dodgy chemicals. And turning over huge land areas to mono-culture crop growth. And global climate change - this has the earliest reference to the Greenhouse Effect of any piece of fiction I've read, as far as I can remember. Really, this is the fictional equivalent of the extra-ordinarily influential popular science work, Silent Spring. Other SF writers were working on the general environmental theme and the problems of bio-accumulating insecticides specifically back then, The Green Brain being a prime example. Other major problems facing humanity and indeed, much of life on Earth, were also being tackled back then, for instance population control, in A Torrent of Faces, a lesser known but tremendously fun James Blish novel in which a society trying to cope with a human population of one trillion is examined.
So, all those problems, understood back in the sixties - how many of them have we solved? And how many have got worse?