For much of grad school, "The Hitchhikers Guide" served that purpose. Same with some of the later Harry Potter books. And Bill Bryson's "A Brief History of Nearly Everything".
I also re-read the comics "Kingdom Come" and "The Dark Knight Returns" on a regular basis.
I always tell myself I'm going to skip the last one, because it's such a downer. (He wrote it during his divorce.) But I keep reading it because despite being such a downer, it's still eminently readable.
I also re-read the comics "Kingdom Come" and "The Dark Knight Returns" on a regular basis.