The quick defenition of an eTextbook is an electronic textbook. A textbook is electronic when your copy of it is digital (or obtained from a digital source), and not a bound traditional textbook one would buy at the bookstore. For example, rather than carrying your physics textbook to class, you carry your tablet with your physics book loaded on it. Depending on where you get your eTextbook, sometimes there are also options for printing, or ordering a printed bound copy.
The most common way students are accessing eTextbooks now is through eTextbook online suppliers, such as CourseSmart, Inkling, or Chegg. These textbooks are accessible from devices such as computers, tablets, smartphones and sometimes eReaders. In this case, students are likely assigned a traditional book for one of their classes, but they go to these providers for the option of renting/buying it in eTextbook form.
Faculty can seek out eTextbooks to use on their own, or request a digital option through the University Book Store. For more information about this, contact your campus' University Book Store.
Open Source Textbooks
Open source textbooks (or simply open textbooks) are online textbooks which are released under licensing that allows instructors to access, distribute, or modify the textbook's content (eliminating chapters which will not be used, adding instructor notes, etc.) for little or no cost. This, in turn, allows students to also access the materials at little or no cost. Of course, this depends on the license the individual has put on their book, but this applies to most open textbooks at the moment.
Open textbooks, along with eTextbooks, are an emerging technology. Although they provide a low-cost alternative to the traditional textbook, there is some debate around the quality and credibility of open textbooks. With some sites, anyone can write their own textbook and self-publish it on an open textbook site. Currently, there is discussion going on about how to best analyze these books for credibility.
Open Textbook Sites
Connexions: With Connexions, learning professionals create "collections"- a term which is broadly used and can mean eTextbooks, full courses, journals, or whatever the author wishes them to be. These collections are made up of modules, which are short lessons, assignments, labs, etc. The collections and modules are downloadable for offline reading in either PDF or EPUB formats. Both are compatible with most eReaders (note: the Kindle will not read EPUB format, only PDF. However, most other readers should be able to recognize either one.
Flat World Knowledge: Flat World Knowledge is a popular and flexible open source textbook site. It allows instructors to select a textbook and adopt it for use in their class. Students can access to the books by registering on the site and either 1) reading them online, 2) printing copies out themselves, 3) turn the books into audio files, 4) ordering them as an eBook, or 5) ordering hard copies of the books in color or black and white for $1.99/chapter.
Textbook Media: Certain books from publishers are licensed to Textbook Media so that the user can access them for very cheap- or free! The books are available in the combinations of different formats, including a sponsored or non-sponsored online book, a PDF file, a printable book, a pre-printed book, or smartphone apps.