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.
Comments 5
This bug will always exist until Mojang adds a new line character. Checking on snapshots updates will yield little results.
With the changes to the 'pages' tag having access to the JSON text component, you can use the newline character \n to insert a newline (in 14w25a):
/give @a written_book 1 0 {title:"Test",author:"test",pages:["{text:\"Line 1\nLine 2\"}"]}
This will be needed for mapmakers!