For details on earning the title for yourself, see RuneScape:The Wikian.
The Wikian book is an unique item used to grant the title [Name] the Wikian. It cannot be obtained anywhere in the game, only directly added to the player's account by a Jagex Moderator.
The title is granted by using the book on the other player - similar to inviting to a clan. This prompts a confirmation message, and once confirmed the recipient is immediately granted the title. Upon receipt of the book, the title is granted to the owner (as you can't use the book on yourself).
Trivia
- The Wikian book is one of, if not the rarest item in the game, with only one player owning it.