iBooks Author - iBooks Author, free from the Mac App store, allows you to create beautiful Multi-Touch textbooks — and just about any other kind of book.
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Mobipocket eBook Creator - Mobipocket eBook Creator is one of the easiest way to create a professional level of eBooks by simply providing some HTML and image files to your publication.
Invision - Prototyping and collaboration for design teams
Atavist - Atavist provides a suite of publishing tools to tell stories and build websites.
Sketch - Professional digital design for Mac.