The Old Book is a relic that first appears in Kingdom Hearts. It is in the possession of Merlin and whenever the book is read, it transports the reader into the world of 100 Acre Wood.
Story
Kingdom Hearts Birth by Sleep
In Radiant Garden, Merlin accidentally drops the old book on his way home. Terra picks it up and delivers it to Merlin, but he claims to have never seen the book before. Afterwards, Merlin decides to keep the book in his house and allows Terra to view it at any time. Later, Merlin extends this permission by allowing Ventus and Aqua to see the book too.
Kingdom Hearts
While on his second visit to Traverse Town, Cid asks Sora to deliver the old book to Merlin. After it is delivered to Merlin's House, Merlin explains that the book has pages torn out that Sora can recover to restore the full Hundred Acre Wood. Merlin leaves the book in his house and allows Sora to look at it at any time. Over the course of his journey, Sora eventually retrieves all of the torn pages and puts them back in their rightful place.
Kingdom Hearts II
Merlin takes the book with him when he moves to live in Hollow Bastion. A group of Heartless attempt to steal the book but they are handled by Sora. Unfortunately, the book was damaged during the battle and pages have been torn out. During his adventures, Sora manages to find the missing pages and fixes the book once more.
Other appearances
Kingdom Hearts: Chain of Memories
The book appears as the world icon of the Hundred Acre Wood.
Gallery
<gallery> File:100 Acre Wood KHBBS.png|The book in Kingdom Hearts Birth by Sleep. File:100 Acre Wood KH 2.png|The locked book in Kingdom Hearts and Kingdom Hearts Re:Chain of Memories. File:100 Acre Wood (Card) 1 KHRECOM.png|The world icon in Kingdom Hearts: Chain of Memories. File:100 Acre Wood (Card) 2 KHRECOM.png|The world icon in Kingdom Hearts: Chain of Memories after completion. File:100 Acre Wood KHII 2.png|The locked book in Kingdom Hearts II. File:100 Acre Wood KHII 3.png|The book in Kingdom Hearts II after being attacked by Heartless.