Minecraft wiki entry for Book_and_Quill, associated text: § + k creates randomly changing characters.
§ + l creates bold text.
§ + m creates strikethrough text.
§ + n creates underlined text.
§ + o creates italic text.
§ + 0 – f (hexadecimal) creates colored text.
§ + r resets any of the previous styles so text after it appears normally.