Build a website where you can offer your e-book for sale directly via a PayPal account. Give your book its own personal home on the Web. Buy a domain name that is the same name as your book, or as close to it as possible. Or get a domain of your pen name and feature your book as part of a catalog of your work on the site.
Obtain book reviews -- you'll find websites that cater exclusively to reviewing a certain genre, like The Romance Reviews site. A very important aspect of marketing your book is to find trustworthy people to read and review your book. Research individuals who are experts in the fields related to your book's genre, and then write to them and ask them for a brief review. The bigger and more important the name of the reviewer, the better. Put the reviews on your website.
Visit other authors' websites who have published books similar to yours. These authors are often more than willing to write a review for you. You can also use them as a networking resource by asking them to exchange website links.
Find the small online booksellers. Run a search for small independent booksellers and you will find a huge list of potential sellers willing to virtually stock your book.
Sell your book in e-book format on the websites of the large distributors such as Barnes and Noble, Amazon and Books A Million. Be sure to read the bookseller's contract carefully to see if there are any significant fees.
Find the places online where writers congregate and start networking. There are many such sites on the Internet and they allow you to post a picture of your book cover, sample pages and contact information.