When I read the Southern Reach trilogy (those books that the Alex Garland movie "Annihilation" is based on), I accidentally read them out of order and didn't even realize it until long after I'd finished it all. I read the second book first, then the first one, then the third. They weren't numbered and, at least on those editions, it was really strangely unclear about the reading order. Weirdly enough, I think the books actually work better the way I read them, lol.