The Last Exit
Every world gives her power. Every step takes her further from home.
Each time Reya Drayke passes through a dimensional gate within the Exit, she adapts-literally. The worlds are unstable, and the Exit "downloads" part of each one into her DNA. She starts developing strange powers tied to each world's laws... but they come at a cost.
Her best friend, Kol Mori, dives into the Exit after her-unauthorized and completely unaware of what awaits. He was not prepared. But making sure Reya is alive is enough for him.