I have to admit that listing on Smashwords was one of the hardest things I ever did, but one of the best.
Their guidelines are some of the most stringent of any in the self-publishing industry, but once you've gone through the guide and learned how to get books approved on their site, your book will look good on ANY ebook reader.
That's why I highly recommend starting with Smashwords in self-publishing your book.
Before you begin, download the free style guide referenced above and follow it carefully. Once your book is published and approved for Smashword's premium catalog, you will be able to opt in for several ebook sales opportunities.... downloadable on Apple IPad, Kobo Ebook Reader, Sony E-Book Reader, and more.
To begin, go to Smashwords.com.
Listing Your Book on Smashwords