At Tor.com Larkwood tagged five favorite fantasy multiverses, including:
The Dark Tower series by Stephen KingRead about the other entries on the list.
Oh, The Dark Tower. Stephen King’s fantasy series deals with a legendary gunslinger who rattles through dozens of worlds, including our own, on an endless quest to reach the Dark Tower, and possibly thereby prevent the collapse of all reality. These books are all the more dear to me for being so very sprawling, flawed, nightmarish and bizarre. Should a fantasy series have an evil haunted sentient train? Should it have gun magic? A big talking bear? An apocalyptic-Western-Arthurian-science-fantasy setting? Numerology? Bird-headed people? Should the author himself appear in a cameo along with characters from many of his other books? If your answers to most of the above aren’t “obviously! of course!” then I don’t know what to say to you. Are they good books? I have no idea. The Dark Tower fascinates me. Like [Clive Barker's] Abarat, it’s an epic fantasy rendered with the specialist tools of a horror writer, which might be why it largely falls into the ‘never explain, never apologise’ category of worldbuilding above. The sheer ambitious strangeness is undeniable.
--Marshal Zeringue