15It's Not A Universe It's A Multiverse
It's currently pretty popular to refer to fictional worlds as universes. The Marvel Cinematic Universe, the Tarantinoverse, the Star Wars universe, etc. It's a good term, neat and concise, but for the world of The Dark Tower it just won't do (after all, precious little in The
Dark Tower is neat and even less is concise).
The whole idea of The Dark Tower is that, of a sprawling multiverse, there is a whole slew of alternate universes, worlds packed upon worlds packed upon worlds. The central character, Roland The Gunslinger, the last member of a destroyed civilization, is journeying through them trying to find The Dark Tower. Most of these universes, like the one our hero Roland comes from, are wracked with entropy, falling apart and in chaos (referred to in the book as "Moving On"), a symptom of a sickness within The Tower itself, a sickness that Roland hopes to root out.
The Tower is something of a nebulous concept. It's both the lynchpin of reality, holding these worlds together, and bigger than reality, containing them all within itself. It helps to remember that The Dark Tower, for all its other influences, is very much a product of '60s hippy-dippy New Age thinking. It helps to think COSMIC. Because if a tower that simultaneously contains and exists in all realities sounds strange to you, buckle up, it only gets weirder from here.