In 1971, the first Locus award went to Larry Niven for his creation of an offbeat new type of science fiction world in Ringworld. He did the same thing with The Integral Trees, and, lo and behold, gets another Locus. Ringworld swept the awards though, Integral Trees just won the Locus.
The world of Integral Trees isn’t really a world at all, it’s actually a cloud of gas around a neutron star. In one area, called “the smoke ring” this gas gets fairly dense and is actually breathable. Various plants and birds live in the smoke ring, including the titular integral trees – giant plants that span the entire width of the smoke ring (winds bend each end in opposite directions, causing them to look like integration symbols from calculus). Humans colonized the smoke ring from a slower-than-light starship, and societies have developed both on the trees and on dense vegetation masses called “jungles.” Over hundreds of years, the humans have grown tall from low gravity and developed tribal societies that mimic the traditions of their colonizing forebears (The Scientist is a position like a shaman, for instance). In the novel, we follow one group of tree-dwellers as their home tree disintegrates and they are enslaved by jungle dwellers. It’s short and fast-paced, as the protagonists skip from one strange and harsh environment to another in a series of action sequences.
Whether this physical world is plausible or not, I’ll leave aside (it doesn’t feel plausible, but Niven is the type of hard sf author who certainly did the math). It’s the human world of Integral Tress that rings hollow to me. The societies are generic and dull (the jungle-dwellers are slavers, the tree-dwellers are noble savages), and the characters are too. The best-developed character is Clave, the group leader who is a fierce and loyal warrior, but a bit full of himself. The protagonist Gavving is a decent guy, and his love interest Minya is a tough girl. Most of the cast is completely interchangeable. I really did not care about any of them.
This should have been a short story that introduced Niven’s interesting world and moved on. I have a whole essay bouncing around in my head about how there should be more sf written as faux-non-fiction rather than the author trying to cobble together a story as a vehicle to introduce his "cool Idea" (maybe I'll actually write it out some day)*. This novel was the inspiration for that line of thinking.
* I have three words for anyone who might scoff that this would further lower the literary establishment's respect for speculative fiction: Jorge Luis Borges.