4.5 stars, rounding up to 5. This is only a novella, but it packs so much into its relatively tiny word count that it's dense and varied and complex, using the myth of Atlas and Heracles as a scaffold for history, and the weight of living with it. Personal history, mythic history, the history of the universe and of science, of space travel and sympathies, and it even folds in poor lonely, terrified little Laika and gives her the happy ending she deserved but did not get. This story's all about the potential for endings - for different endings, the ones we can make ourselves - and yet for all the density of its choices there's still something very light and lively about the prose (at least once you get past the opening pages). Well worth reading, I'm going to have to find myself a copy to keep.