Actually, this list is helpful for writers of every description.
Platform by Michael Hyatt - The basic essentials of how (and why) to build a platform. This needs to be read by every writer.
Crush It by Gary Vaynerchuk - Why you should be using Youtube and why now is the best time ever to be an author.
From Entrepreneur to Infopreneur by Stephanie Chandler - Written by a woman who walks her talk, this is the book that explains how to take the knowledge and status gained as an author and apply it to other money-making possibilities. This book made me feel incredibly excited about my future.
The Icarus Deception by Seth Godin - The master's latest book, this one tells us we're all creating art and instead of just talking about it we need to get it out the door for other people to see.
Never Eat Alone by Keith Ferrazzi - This book made me realise how essential and effective networking is. Especially for authors!
Guerrilla Networking by Jay Conrad Levinson and Monroe Mann - Really effective techniques for building strategic relationships and filling your life with inspiring, influential and fascinating people.
The Frugal Book Promoter by Carolyn Howard-Johnson - Excellent all-round advice that is simple and achievable for everyone. If you worked your way through this and did even half of what she details you would find your writing career expanding.
Some of these may also be available as printed books, it's just that I have read them and used them as ebooks.
Show Your Work by Austin Kleon
The Freaks Shall Inherit the Earth by Chris Brogan
31 Days to Finding Your Blogging Mojo by Brian Allain
Blog It by Molly Greene
500 Social Media Marketing Tips by Andrew Macarthey
Blogging the Smart Way by Jeff Bullas
and some others...
The Tao of Twitter by Mark W. Shaefer
Ninja Book Marketing Strategies by Tom Corson-Knowles
Turning Pro by Steven Pressfield
Secrets of the Six Figure Author by by Tom Corson-Knowles
How to Market a Book by Joanna Penn
The Art of Being Unmistakable by Srinivas Rao
APE by Guy Kawasaki
How I wrote 2 Ebooks in 21 Days by Glen Stanford
How to Write a Nonfiction Ebook in 21 Days That Readers Love by Steve Scott
|Joe Konrath's blog is as simple as they come, but it works|
The Creative Penn
Jeff Goins Writer
A Newbie's Guide to Publishing
Publish Your Own Ebooks
|Srini Rao from Unmistakable Creative|
The Creative Penn
Beyond the Book
Six Pixels of Separation
The Author Hangout
Blogging Your Passion
Content Warfare Podcast
The Accidental Creative
Social Media Marketing
This is Your Life by Michael Hyatt
Another Top 10 List of great blogs for authors
Srinivas Rao on being flexible with your dreams