What inspired this question for me was reading Alex Haley’s “Roots” after having just read “Beloved” by Toni Morrison. I thought that the two taken together give a wonderfully detailed image of American slavery and it’s effects on the body (Roots) as well as on the soul (Beloved).
Another that came to mind was Jack Kerouac’s “On The Road” and Hunter S Thompson’s “Fear and Loathing in Las Vegas” as I personally felt that FaL was written as a direct parody and skewering of the kind of transcendentalist optimism we see in someone like Kerouac.
I guess I’m thinking of books that look at similar issues from complimentary angles or books that seem heavily inspired by others and almost responding or expounding, so that you come away having learned more than the sum of their parts.
EDIT: Doesn’t have to be all fiction. Non-fiction is welcome as well.
Anathem by Neal Stephenson and A Canticle for Leibowitz by Walter M. Miller Jr. Both are about science monks coping with an ever-changing world.
The King of Elfland’s Daughter by Lord Dunsany and Stardust by Neil Gaiman. The way it’s written, Stardust could be a kind of sequel to the other novel. They both deal with a human crossing to Faerie especifically to retrieve a woman and bring her back to the world of Men.