Someone wanted to learn this too, so Grasp built them a personal learning path.
You can keep exploring this one or create a path like this one shaped around you.
Recommended resources
Module 2
Core Ebook Design Skills
Module 3
Designing an Eye-Catching Ebook Cover
Module 4
Building an Informational Ebook Interior
Module 5
Crafting a Story & Fiction Ebook Interior
Module 6