I've been using an app called Vellum on my Mac to convert my books for use on many of the popular ebook readers. Each of my books currently available on Amazon were exported using Vellum.
Vellum is as close to what I would call WISYWIG as I've found for the task. It makes the job of dressing up your work easy and does not require any coding knowledge. Honestly, I thought Vellum was a bit on the pricey side at first, but once I began using it in earnest, the price was no longer an issue. I recommend you give Vellum a try.
Available export formats include:
- Google Play