Answer :
Dr.King wants people to know that fighting is not the key to every thing he compared his letter to a book because he wants peace freedom and religion.
In his "Letter from the Birmingham Jail" MLK Jr. says: "Never before have I written a letter this long -- or should I say a book?" matching the length of his letter similar to a book and highlighting the tough circumstances he was undergoing while being debarred from his freedom, without else to do but pouring his thoughts into words.
