Star Wars: The Essential Atlas -

While is a non-fiction reference book, it is designed as an "in-universe" document that weaves together the complex history of the galaxy into a cohesive narrative. It doesn't tell a single linear story like a novel, but rather a "biography" of the galaxy itself through maps, historical timelines, and planetary profiles. The Story of a Living Galaxy

The "story" within the Atlas spans over 25,000 years, chronicling how a sprawling, chaotic universe became the settled galaxy we see in the films: Star Wars: The Essential Atlas