The Rediscovery Of Man [collected short storied] by Cordwainer Smith
I had read that people "either loved or hated" his stories. I did not love them, but I wouldn't say I hated them. The stories have some unique concepts and interesting perspectives. They also frequently had aspects that made me uneasy or rubbed me the wrong way. Some of the stories at the beginning of the history of the "Instrumentality" have central characters who are idealized Prussian young ladies who came from the Nazi era. This put a bit of suspicion in my mind, which did not seem to end up with any real basis. There were peculiar ideas like "the pain of space" that caused problems for people in early spaceships. And bizarre pseudoscientific technology such as flattening spaceships from three dimensions to two dimensions in order to let them go faster than light.
Aside from these aspects, I found the stories to be of a more serious SF nature than, say, Edgar Rice Burroughs’ Barsoom. But I certainly didn't find it to be serious in the sense of Arthur C. Clarke, Isaac Asimov and other writers of note during the same period as Smith. Smith sometimes writes in a simply whimsical way (as in his story of the duck-people who come to Earth with huge appetites for Earth foods and drinks). Often he writes more like a storyteller of an oral tradition than in the style of writers of recent ages. Some stories are tales of significant people of the future being told by somebody living centuries later - that is, they are told as legends.
There is something in his writing that reminds me of fantasy. This is probably partly his talking intelligent animal-people characters. Perhaps it's partly that his storyteller style and legends leave hints of "olden times" in my mind. And his stories often have a mix of some things using advanced technology and some things being done the way they were in pre-industrial days. But I think there is something else that is not explicitly fantasy which shares something that is more common in fantasy than SF.
On the other hand, some of the stories have spaceships using solar sails. I think this was forward thinking for his time. And at least those stories take seriously the issues of relativistic and FTL travel.
I listen to books on tape while riding on a commuter train to and from work. I found with this book as with some others, I tended to nod-off or fade out on a number of evening trips home while listening to this. It's just not a book that holds my attention to the degree that most books I choose do.