Deepness in the Sky is the best. so many ideas being thrown out that are amazing in that book. A Fire Upon the Deep is kind-of related to it and is also quite good. Children of the Sky, the follow up to A Fire Upon the Deep... not as good. it's about a medieval society of group-think wolf-creatures. they require multiple creatures in concert to be able to become smart, communicating with each other telepathically
Rainbows End is about our soon-to-be future, with nothing in it that i think is out of the question
vernor vinge, a computer scientist, predicts the singularity will occur in 2030. it's about recursive self improvement in AI, causing an intelligence explosion, and anything beyond the singulatirty is impossible to predict. many of his novels deal with it. the guy has won the hugo multiple times and his books are all generally quite good.
Alistair Reynolds has a bunch of one-off novels and then his two space opera series, Revelation Space (dark, involving eradication of the human race) and Poseidon's Children (not so dark, involving humanity on the cusp of interstellar travel). this guy used to work for the ESA, and all of his stories are realistic. he deals with hive consciousness, plagues that infect man and machine (which had melded themselves), and in one book has a society where thousands of space platforms surround a system where anything can be imagined. some people willingly submit themselves to nazi like authority, others are furries (biologically modified), others shut themselves off from the future internet, religious cults around hero/villans, etc etc. he has rich amazing stories, almost none of which involve aliens (and if they do, they are robots), but the humans themselves are very alien to one another as they spread throughout the galaxy
but if you want space opera TV, Battlestar Galactica saz. trust me. it was an amazing platform for dealing with political issues, such as the militarization of the police, use of torture, the outting of people, with religion... and it has a military backdrop to all of it with special effects that are quite well done