Vellum 2.6.3 | Mac OS X | 13 MB. 

Vellum is an eBook-generating tool that lets you easily create an eBook from a text manuscript or from scratch within the application. Choose the appropriate style from several options, view instant previews of the finished product, and easily generate and regenerate eBooks with a single click to avoid disaster upon finding mistakes.

Compatibility: macOS 10.12 or later 64-bit