The essays Craig Mod publishes on his site are always educational, often inspiring. Of those I follow, he’s leading the way in the future of publishing. Just as developing an iOS app has been a path to self-employment in recent years, so too is self-publishing.
If you’re considering writing a book, e-book or otherwise (is there much difference these days?), you’d do well to read this piece from Craig. He outlines the work and thought required in publishing a book in the various formats and within the various platforms that are currently available.
When you’re done that, read his other helpful longform articles.