Hothouse is set in the far future of Earth. The Sun has expanded, and is nearly ready to go nova. The Earth and the Moon are now both in tide-locked orbits, so that each keeps one face continually toward the Sun. The bulk of Earth's sunward face is dominated by a huge jungle, mostly composed of a single banyan tree, which has been colonized by any number of weirdly evolved plants. Very few animal species remain, and the plant species have adapted to fill many animal niches. For example, the Traversers are huge spider-like plants, which have built webs between the Earth and the Moon. (The book is not an example of hard science fiction, to say the least -- one of the absurdities is that the according to Aldiss' conception, the Earth and the Moon are at corners of an equilateral triangle with the Sun, which is necessary for them both to be tide-locked -- but which also means that the webs of the Traversers span some 93,000,000 miles -- 250,000 miles, I had thought, was wacky enough! I should add, however, that scientific verisimilitude is in no way a goal of this book, and as long as the reader doesn't try to find scientific rationality behind Aldiss' ideas, he will be enchanted by the imaginative vigor behind them.) Aldiss' descriptions of the various plant species, the remaining animal species, and of the ecology of this future Earth are tremendously interesting, clever, and colourful: his imagination is fully as fecund as his future "hothouse" world.

One of the few animal species which has survived is humans, in several much-altered forms. The novel follows Gren, a young male member of a tribe living in the jungle. The opening segment tells of a crisis in the tribe's existence: its leader decides that she and the other adults are too old, and must "go up," leaving the tribe to the just-maturing children. We follow the adults on their curious journey "up," which seems at first simply a euphemism for death, but which turns out to mean something quite different. Then the book abandons them to follow the children, particularly Gren, who rebels against the new leader, and takes one of the girls with him on an unexpected journey. Gren finds himself "colonized" by an intelligent fungus, who has plans to use humans to control the world. The fungus leads Gren and an ever-growing and contracting band of allies on a journey to "Nomansland," the border between land and ocean, then across the ocean to a strange island and finally to the dark side. Aldiss both follows SFnal tradition by having this journey be a journey of discovery about the true nature of this world, and subverts tradition by his description of Gren's character, his reluctance to learn, and his ultimate desires once he has learned the truth about Earth's future.

The greatest strength of this book I have already mentioned: the constantly delightful inventions of new plants and animals and life-cycles. None of these are terribly plausible, but they are consistently fun and clever. Gren is not the most admirable of characters, but somehow he and his companions become likable. The book is also quite funny in many places, sometimes ribaldly, sometimes satirically. The non-human intelligences, such as the fungus and another being who shows up late in the book, are also delightfully off-centre. The plot is resolved very well, and we are left with a nicely complete description of the strange "Hothouse" Earth, as well as intriguing hints about the rest of the universe and the future. A very fine book, and a worthy award-winner.