While Papeair is for both Windows and MAC, here is another service for formatting ebooks that has been around for a long time.
VELLUM
Vellum’s built-in Book Styles has classic touches like custom drop caps, ornamental flourishes, and are automatically applied to your book. They are tailored for each store and adapt to screens large and small. Upload you ebook to Kindle, iBooks, Google Play, and more
Click below to see Vellum in action!