Cytonic

Spensa Nightshade has spent two books fighting for the Defiant Defense Force and for her people, and now she chooses to go where almost no one can follow: the Nowhere, the dimension that makes faster-than-light travel possible. Hoping to give her friends a fighting chance against the Superiority, she sets out across its floating fragments of land, past pirate-held territory and toward the central lightburst, with her AI companion M-Bot and her odd pet slug Doomslug for company.

Along the way she meets a stranger who says he is an explorer who lost his memory after a very long time in the Nowhere, and she starts collecting memories that explain where cytonic powers come from and what the delvers really are. This third Skyward novel is quieter and stranger than the dogfighting of the first two, trading flight combat for exploration and answers. It follows Skyward and Starsight, and the final book is Defiant.