An electronic book (variously: e-book, eBook, e-Book, ebook, digital book, or even e-edition) is a book-length publication in digital form, consisting of text, images, or both, readable on computers or other electronic devices. Although sometimes defined as "an electronic version of a printed book" many e-books exist without any printed equivalent. Commercially produced and sold e-books are usually intended to be read on dedicated e-readers. However, almost any sophisticated electronic device that features a controllable viewing screen, including computers, tablets and smartphones can also be used to read e-books. (1)
Companies that provide E-Book Publishing Services:
Blurb: http://www.blurb.ca/ebook?gclid=CPTilbOTz8gCFQUHaQodt_4IaA
E-PubBud: http://www.epubbud.com/
Friesenpress: http://welcome.friesenpress.com/ebook?gclid=CK2A862Vz8gCFYRFaQodqmAHHg
Scribd: https://support.scribd.com/hc/en-us/sections/202246366 ; You can "publish" anything you write by just uploading it to Scribd documents, of which there are currently millions in their database.
Smashwords: https://www.smashwords.com/ Smashwords in Wikipedia: https://en.wikipedia.org/wiki/Smashwords ;
Wikipedia Category "Ebook Suppliers": lists many e-book publishers, including some like Docstoc that have closed down: https://en.wikipedia.org/wiki/Category:Ebook_suppliers
References: (I have five books in Scribd that I can read on E-Book publishing;)
There are numerous free PDFs on Google about how to publish your own E-book: https://www.google.com/webhp?ei=T-DwVPm6BMGrggT6zYPQCQ&yv=2&rct=j#q=how+to+publish+your+own+ebook+filetype:pdf
Coker, Mark (founder of Smashwords), An Introduction to Ebook Publishing, YouTube Video, Sept., 2013, 1 hr. 42 minutes.
Komando, Kim: http://www.komando.com/tips/12282/publish-your-own-ebook-and-make-money/all
Magbooks.com: How to publish Your Own E-Book: http://www.magbooks.com/product/how-to-publish-your-own-ebook/ Not free; 2.99 British pounds;
Wikipedia E-book page: https://en.wikipedia.org/wiki/E-book