For ebooks there is Inklewriter which is pretty neat. All done via a web interface - http://www.inklestudios.com/inklewriter
The technical frontier of digital art is no longer what computers can do, but how we get them to do it.
Today, digital artists can choose to work with a profusion of advanced hardware options (fast processors, graphics cards, sensors, etc) and some wonderful open source code libraries — but when it comes to environments for authoring their artworks, their choices are remarkably few. With this open source project we hope to expand the possibilities open to artists.