I’ve reccomended Cloud Atlas countless times and now I reccomend the prequel - Ghostwritten, even more.
These books are like no other. They are more ‘like no other’ than most books for which ‘like no other’ is true. They make you think outside the box, beyond normal parameters, even outside normal reality sometimes. They make you question your own self-assured belief of existence.
I have a particular fondness for ‘Cloud Atlas’ because I read it first, but Ghostwritten seems to excercise the brain more. Probably worth reading them in order.