When typing a give command to give the player a writable book, there is no way to implement a new line.

give @a written_book 1 0 {display:{Name:"Bug Report Book"},pages:["There is no way to issue a new line except by using spaces                                                   like this."],author:"Jira"}

Using blockdata on a book in a chest shows there is a [LF] icon but it cannot be copied into a command block.