Ringworld is a book whose scale, dimensions, structures are difficult to get a true sense of scale on. Imagine for a second, the creation which Larry Niven uses to base the majority of his book upon - a vast ring, circling around a sun, nearly three hundred kilometers in diameter and a billion kilometers long, producing a quantity of space which is simply incomprehensible to the human mind. But Niven also uses it as a way to play around, convincingly, with equally incredible feats of probabilities, chance, and luck - and has the skill to construct a narrative and world where this all makes perfect sense.
The sheer grandeur of the ringworld is astounding and gives Niven a brilliant field for an expansive imagination. Niven dreams up all sorts of things in his book, with floating cities, patches of world-destroying sunflowers, the problems of long-life and sociability and interaction with others, social homogenization, and population growth. There is so much and the way that Niven writes that there is a rushed and frantic feeling that pervades the pages: that it jumps from one scene to another, with little interest in if the reader is following along, why things happened, that Nivens is so overjoyed to spill out his ideas that he just is taking you along for the ride. It becomes confusing at times, although it does provide for an expansive view on a mixture of what were contemporary concerns at the time (overpopulation) and some of his own ideals: it is a fascinating mixture of both almost retrograde and far futuristic concepts.
But the other elements which he plays around with are principally evolutionarily. Humans and aliens are united by the great question of evolution - of what the future of theirs species is. Kzin notably have been tamed to an extent by humans, their brutal bloodlust beaten out of them by incredible casualties that they sustained. But the humans too are given the grace of good luck - something which their ring world counterparts didn't possess. The future of human evolution has been discussed in various books: what is striking in this is that it is largely directed by external events, rather than being human directed as many contemporary works provide.
I have my doubts about this technological collapse posited by the book. Any superconductor-eating bacteria, posited as responsible for the destruction of the Ringworld's technological system, would have been a slow and scattered plague. The Ringworld is an incredibly massive, incomprehensibly so, engineering project, and it would have had a vast number of superconductors, used for the power transmission systems, and these would have been distributed across the ring. There would have been time for alternate solutions to be determined and resolved, and the destruction of civilization caused by a bacteria seems unlikely to me. It is also a strangely empty universe, although again this speaks to Niven's time: barely 40 billion humans despite multiple worlds, when far more could be supported with interstellar technology.
Writing aliens is an incredibly difficult task. Writing a human is hard: writing someone who comes from an entirely different cultural origin is even worse, and when you throw in differences of biology and evolution it gets exponentially more complex. If I had to choose a single thing from Ringworld which is brilliantly handled, it is the way that the alien species - the puppeteers, the Kzin, even the ringworld inhabitants and engineers, as well as our own culture's evolved products that might as well as be aliens - are written. They are genuinely distinct, different, truly alien - the Kzin with their fierce, warlike, honor based society and reactions that to humans seem bizarre and uncalled for, the puppeteers with their herd mentality, paralysis in front of fear, their scheming and manipulative nature, the creators of the ringworld with their infinite patience and distinct psychological profiles drawn from their great length of life and the nature of their interstellar transport technology. Nivens carries out different species with panache.
Of course, this leads into the potential problem of characters not being, well, characters, but rather a type. This is a fair accusation to throw against him, since in order to make them work as aliens it is necessary to play off their main theme. But at the same time given the sheer difficulty involved in writing aliens it is easy to see why the choice was made.
Ringworld is an engaging adventure of survival, of a massive and ancient universe, of the ruins of civilization and of interaction between man and alien. It's exploration in the finest sense of discovery an increasingly more complex world, married with action and an examination of concepts of evolution and parallel technological development. As a classic in science fiction's anthologies, it is still a great read.