An electronic book (or e-book) is a book publication made available in digital form, consisting of text, images, or both, readable on the flat-panel display of computers or other electronic devices. Although sometimes defined as "an electronic version of a printed book", some e-books exist without a printed equivalent. Commercially produced and sold e-books are usually intended to be read on dedicated e-reader devices. However, almost any sophisticated computer device that features a controllable viewing screen can also be used to read e-books, including desktop computers, laptops, tablets and smartphones.
In the 2000s, there was a trend of print and e-book sales moving to the Internet, where readers buy traditional paper books and e-books on websites using e-commerce systems. With print books, readers are increasingly browsing through images of the covers of books on publisher or bookstore websites and selecting and ordering titles online; the paper books are then delivered to the reader by mail or another delivery service. With e-books, users can browse through titles online, and then when they select and order titles, the e-book can be sent to them online or the user can download the e-book. At the start of 2012 in the U.S., more e-books were published online than were distributed in hardcover.
The main reasons for people buying e-books online are possibly lower prices, increased comfort (as they can buy from home or on the go with mobile devices) and a larger selection of titles. With e-books, "[e]lectronic bookmarks make referencing easier, and e-book readers may allow the user to annotate pages."  "Although fiction and non-fiction books come in e-book formats, technical material is especially suited for e-book delivery because it can be [electronically] searched" for keywords. In addition, for programming books, code examples can be copied. The amount of e-book reading is increasing in the U.S.; by 2014, 28% of adults had read an e-book, compared to 23% in 2013. This is increasing, because by 2014 50% of American adults had an e-reader or a tablet, compared to 30% owning such devices in 2013.