The search for extra-terrestrial life tends to focus on the requirements for life on Earth: carbon, oxygen, liquid water, and so forth. There are arguments that support the idea that any life would have similar needs. Yet there are also arguments that life could be so alien that we might not even recognize it as life. Indeed, the biological definition of life can be interpreted to include things like stars, which are generally not considered "alive."
I love classic, hard science fiction (we've talked about the difference between hard and soft science fiction before). Verne, Wells, Asimov: I've read most of what they wrote. These stories, exploring scientifically rigorous possibilities and ideas, hold a unique place in the huge volume of work classified as science fiction. To use the MICE quotient, these are idea stories, through and through. I'd heard about Ringworld in a few different places, and decided that this was something I needed to read.