Cloud Atlas — David Mitchell (2004)

David Mitchell's Cloud Atlas is the most technically ambitious British novel of the century: six nested narratives spanning from the Pacific in 1849 to a post-apocalyptic Hawaii in the far future, each written in a completely different style, with each story interrupted at its midpoint before the second halves are told in reverse order. Its argument — that all human action ripples across time, that we are all simultaneously oppressors and liberators — is as daring as its structure.