Hothouse is Brian Aldiss' 1962 novel of runaway global warming in a far-future Earth. The sun has swelled and its radiation has mutated and accelerated the growth of the plant life on Earth, at the expense of almost all animal life. Mankind is one of the few mammals left, but he is a shrunken, nervous creature devoid of all but the simplest tools and language. Aeons have slowed the rotation of the Earth and Moon and they are now locked in orbit, with one side of the Earth in permanent sunshine, the other in darkness.
The novel starts promisingly, with a young tribe of tree-dwelling humans fighting over their leadership as the oldest matriarch decides it is time for her to go 'up' - above the tree line and presumably to her death. Young Gren is forced out of the tribe in the power-struggle, and the novel follows his journey as he explores his strange world, meeting other humans and near-humans along the way.
Though Aldiss is undoubtedly creative, the biggest problems with Gren's journey are that it isn't particularly interesting, and that it comes to no particular conclusion. Aldiss is also pretty inconsistent - the world-spanning Banyan tree doesn't really cover the world at all; the forest-dwellers, who have lived in the trees for countless generations without buildings, suddenly spot something that "looks just like a castle". The biggest flaw is the nonsensical mile-long walking spider-plants that have spun a web between the Earth and the Moon which the matriarch travels along when she goes 'up'.
After all Gren's wanderings, and the promise of travel to the stars, Gren gives up, the novel falls flat, and the reader is left wondering what might-have-been. Aldiss clearly had no plan or shape to Hothouse when he started it.
A novel, intriguing premise let down by lack of planning, structure or story.