Like Iain M. Banks, he set most of his work in a rich, whimsical, hedonistic post-scarcity society that nonetheless dealt with serious threats with merciless efficiency. Like Banks, he explored themes of personhood, cruelty and compassion. Both displayed extravagant imaginations that could invent an ancient ruined processional highway above the clouds leading to a prophetic machine of forgotten origin, or a civilization living in a titanic replica of a castle so enormous in scale that the rooms are kilometers across and climbing the furniture is a feat of mountaineering.
Here is a taste of Smith from the short story Under Old Earth. The dying Lord Sto Odin is going to wager the remnants of his life against an existential threat to Earth, far beneath its surface:
Go he did. He used one of the most peculiar conveyances ever seen on Earth, since his own legs were too weak to carry him far. With only two-ninths' of a year to live, he did not want to waste time getting his legs re-grafted.At his best, Smith was eccentric, imaginative and deeply moving. This is one of my favorite stories, along with The Dead Lady of Clown Town and Alpha Ralpha Boulevard.
He rode in an open sedan-chair carried by two Roman legionaries.
The legionaries were actually robots, without a trace of blood or living tissue in them. They were the most compact and difficult kind to create, since their brains had to be located in their chests—several million sheets of incredibly fine laminations, imprinted with the whole life experience of an important, useful and long-dead person. They were clothed as legionaries, down to cuirasses, swords, kilts, greaves, sandals and shields, merely because it was the whim of the Lord Sto Odin to go behind the rim of history for his companions. Their bodies, all metal, were very strong. They could batter walls, jump chasms, crush any man or underperson with their mere fingers, or throw their swords with the accuracy of guided projectiles.
The forward legionary, Flavius, had been head of Fourteen-B in the Instrumentality—an espionage division so secret that even among lords, few knew exactly of its location or its function. He was (or had been, till he was imprinted on a robot-mind as he lay dying) the director of historical research for the whole human race. Now he was a dull, pleasant machine carrying two poles until his master chose to bring his powerful mind into bright, furious alert by speaking the simple Latin phrase, understood by no other person living, Summa nulla est.
The rear legionary, Livius, had been a psychiatrist who turned into a general. He had won many battles until he chose to die, somewhat before his time, because he perceived that battle itself was a struggle for the defeat of himself.