In middle school I read a LOT of books, but some of the ones that really stuck with me have to do with multiverse theory...
Timeline by Michael Crichton
His Dark Materials (The Golden Compass/Northern Lights, The Subtle Knife, and The Amber Spyglass) by Philip Pullman
The Myst Reader (The Book of Atrus, The Book of Ti'ana, and The Book of D'ni) by David Wingrove with input from Rand and Robyn Miller
Crichton's quantum physicists target an echo of the 14th century France, almost identical to our reality, with one specific difference, a single figure mythical in our world. It is not explored how much variation the physicists can achieve in their target realities.
Pullman's knife-bearer learns to sense differences between worlds before cutting windows into them, providing a degree of control and choice, but still leaving a degree of random chance.
The Millers' Writers, when trained appropriately can craft nuanced and detailed descriptions of Ages that have existed, do exist, or will exist somewhere in an infinite reality. Contradictory descriptions create Links to unstable Ages, while subtle redundancies can reinforce intentional characteristics and traits. These Writers do not create worlds, but bridges to worlds through descriptions of their creative intent. If it can be described, it has the possibility to exist, however briefly, somewhere and somewhen. This great degree of control can be intoxicating and must be honed through restraint and careful intent.
Ultimately, these works all tackle the concept of the butterfly effect in wildly different ways. I find them to be fascinating ways of allowing established POV characters who are relatable to the reader to be thrust into new and diverse worlds and question the interconnectedness of reality.
If you're a fan of the sci-fi trope of alternate dimensions/universes/timelines etc, give these novels a shot. The Wheel of Time does it a bit too, but it's like a 5th string plot line in a 14 book series, so maybe put that on the back burner until you have the energy.
