Which work of science fiction explores the concept of the multiverse through the story of an agent navigating between different realities?

The number of the beast

Robert A. Heinlein, in "The Number of the Beast," takes us on an adventure through the multiverse, a fascinating concept that suggests the existence of multiple parallel universes. The story follows four characters who use a machine capable of traveling through these alternative realities, exploring worlds derived from literature and the author's imagination. This work blends science, literature, and adventure, raising questions about the nature of reality and our perception of the universe. Heinlein is known for his skill in weaving complex scientific concepts with deeply human narratives, and "The Number of the Beast" is a striking example of this mastery.