Sci-fi for me has to be advanced, but believable. The wondrous thing about Iain M. Banks' books about the culture, is that everyone has very human, or at least very believable, instincts, even if they have four arms (the lady with four arms happens to play a double-bass reincarnation, grounding her in my mind as 'humanic'). The Idirans have human ideals about honour that you could find in soldiers.
I quite like humour (who doesn't?), and one great plot was when they (no need to know how) went to a planet called Ea (a with umlaut)... they had a 'king', with an entourage that the protagonist thought was wasteful - "why waste money getting people to stand around all day?". On a night-time visit, they went to the backstreets, and saw a one-legged beggar. Took me ages to realise that Banks was describing Earth, but he did it so masterfully... he really took the p*ss out of Earth and its inhabitants. Although calling the planet Ea was too close to Earth
Anyway, their tech...
super-dooper computers, called Minds, that were far faster and more intelligent than even the brightest of humans. They've developed sentience, and thankfully humour as well! Lasers, etc. in abundance... spaceships housing 400bn people, 2km deep, 40km long, etc., hovering drones with aura fields to display emotion (like pets and tails you could say); Subliming involves moving humans into a digital world, a different kind of dimension...; the ships can fly 'under the skein of space and time' (don't understand
); and finally wormholes everywhere. Turns out LaGrange points (points of zero resultant gravity) can be found at the centre of gas-giants - and tunnels to the centre are plausible.
Sorry for bumping, I believe someone says I can?