Side by side with the paper textbooks there exist the textbooks produced in electronic format (e-books). An e-book is the digital media equivalent of a conventional printed book. Such documents are usually read on personal computers, or on dedicated hardware devices known as e-book readers or e-book devices.
Copies of paper books, produced in electronic format. One can find in Internet a great number of paper editions (books, magazines, manuals, encyclopedias) scanned and posted to website.
Electronic magazines and books (free of charge). Spread of books and magazines in Internet, as a rule, is made for advertising purposes. In such editions there is a Web link of the resource creator. Placed in a text of edition, it is advertised by users, mentioned in forums and blogs, and on different sites.
Electronic magazines and books (requiring payment). Such e-books are made for the next resale. As s rule there is no water bewitched and they come short of volume in comparison with printed editions.
Advantages of e-books:
Quickness of publication.
Ease of renovation in case of the information obsolescence.
Low financial costs.
Right of resale (being bought a book can be sold again according to copy rights).
Very quick delivering after payment.
Possibility of audio and video additions illustrated text material.