17. The system of claim 16 , wherein the mobile device further comprises a display, wherein the display is configured to: output, when displaying a list of e-books with auxiliary content, identification marks indicating e-books that have auxiliary content, and output at least one of a list output screen or a text output screen, wherein the list output screen shows, when the e-book has e-book auxiliary content, pages and words, serving as items, included in the e-book auxiliary content, according to a user's inputs, and wherein the text output screen shows the words to which the e-book auxiliary content are applied, displayed differently from other words on a same page of the e-book.
17. The system of claim 16 , wherein the mobile device further comprises a display, wherein the display is configured to: output, when displaying a list of e-books with auxiliary content, identification marks indicating e-books that have auxiliary content, and output at least one of a list output screen or a text output screen, wherein the list output screen shows, when the e-book has e-book auxiliary content, pages and words, serving as items, included in the e-book auxiliary content, according to a user's inputs, and wherein the text output screen shows the words to which the e-book auxiliary content are applied, displayed differently from other words on a same page of the e-book. 18. The system of claim 17 , wherein, when a particular item comprising the word and page is selected on the list output screen, the display is further configured to output at least one of: sub-items included in the selected item; or information regarding a map that displays information regarding a route connecting a place location corresponding to a word, selected on a previous page, to a place location corresponding to the currently selected word on the currently selected page.