Let’s not overlook the social satire angle. 'The Possibility of an Island' by Michel Houellebecq (a divisive pick, I know) involves a future where a cult clones its members across generations. The 'multiverse' is temporal and genetic, exploring different iterations of the same consciousness in vastly different future societies. The worldbuilding is in the bleak, hedonistic, and then sterile futures each clone inhabits.
It explores the multiverse of the self, asking if a copy of you in a different world is still you, and what that means for love, memory, and purpose.