I've been building and editing ebooks for just over four years now. I started back in 2010 with Macworld when we were still hand-compiling HTML files; and though our process changed and simplified greatly over the years, we still needed multiple programs and long working hours to put everything together for multi-platform ebook releases.
Enter Vellum. I got my first glimpse of the Mac app two years ago back in its early beta stages: At the time, the WYSIWYG ebook-builder only supported text and limited styling, but its live-preview engine and instant-compile for iBooks, Kindle, and Nook gave me true hope for a great cross-platform ebook tool. Vellum 1.0 launched this January with those limited tools, and image support promised down the road. 11 months later, the company has delivered on that promise.