A digital book (electronic book or e-book) is any informational content, similar to a book, in digital format that can be read on electronic devices such as computers, PDAs, e-readers, or even cell phones that support this feature. [MOTA, MO; GOMES, DMOA. An analysis of consumer behavior in the adoption of technological innovation: a Brazilian perspective on electronic books. Revista de Negócios, v. 18, n. 4, p. 3-16, 2013, available at [link], accessed on 23/04/2014]. The most common ebook formats are PDF, HTML, and ePUB. The first requires the well-known file reader Acrobat Reader or another compatible program, while the second format needs an internet browser to be opened. Epub is a standard digital file format specifically for ebooks. Because it is a low-cost storage device and easily accessible due to the spread of the Internet in schools, it can be sold or even made available for download on some free Internet portals.