One of the author's five favorite sagas about alternate timelines and parallel universes, as shared at Tor.com:
The Chronicles of Amber by Roger ZelaznyRead about the other entries on the list.
Beginning with Nine Princes in Amber (published in 1970), Zelazny’s ten book series puts the fun into dysfunctional families. Corwin of Amber, our initially-amnesic protagonist, is one of the ten bickering children of the king of Amber, the ur-kingdom that casts endless shadows—by which I mean other worlds—upon the abyss of Chaos. The family have inherited paranormal powers—the ability to walk through shadows to any world they can imagine, uncanny healing, remarkable longevity—but what they don’t possess is amity: their backbiting and feuding can be lethal. The godlike King Oberon is missing, the fate of the universe is in jeopardy, and…they’re the type specimen for parallel universe travel in fantasy. These are short books, written with Zelazny’s characteristic elan and playfulness, and published between 1970 and 1991: and while they’re very much of their time (30-50 years ago) they haven’t aged as poorly as many other works from the same period.
--Marshal Zeringue