I bought two books the other week which, slightly to my surprise, turned out to be isomorphic.

The Years of Rice and Salt, by Kim Stanley Robinson, is an alternate history novel depicting what might have happened if Europe had been wiped out by plague at some point around the end of the first millennium, and the various cultures east of there – China, India, the Arabs – had expanded into the space, discovered America, and written the history books their way instead of ours. The story spans a period of time orders of magnitude longer than the lifetime of any individual character, and is told as a sequence of connected short stories in which the characters of each one have some sort of connection to the characters in the last (because they're reincarnations of the previous lot in accordance with an appropriately generically-Eastern theology).

Evolution, by Stephen Baxter, is a novel dramatising the evolution of humanity, starting at small ratlike mammals just before the dinosaur extinction and continuing aeons past the present day into what Earth might look like after humanity as we recognise it is long gone. The story spans a period of time orders of magnitude longer than the lifetime of any individual character, and is told as a sequence of connected short stories in which the characters of each one have some sort of connection to the characters in the last (because they're their descendants, hundreds or thousands of generations later and considerably evolved).

This isn't a criticism; both are perfectly good books, they're very different in every detail beneath that basic structural similarity, and there is certainly room in the world for both of them. But it struck me as an entertaining coincidence that I happened to pick them both up during the same trawl of a charity shop. I wonder if the same person donated both of them for the same reason!