Here's the breakdown:
* Lost Memories: Sora, Riku, and Kairi lose their memories of each other and their adventures multiple times throughout the series due to the manipulations of villains like Maleficent, Ansem, and Xehanort. These memories are crucial to their journey and overcoming the darkness.
* Lost Pages of the Book of Prophecies: In Kingdom Hearts: Birth by Sleep, the Book of Prophecies is a powerful object that foretells the future. Some of its pages are missing or corrupted, leading to confusion and misunderstandings about the true nature of the Keyblade War and the events to come.
There is no specific book with "lost pages" in the Kingdom Hearts games. The closest analogy would be the Lost Memories, which are fragmented pieces of Sora's past that need to be recovered.
If you're interested in learning more about the Kingdom Hearts lore, I recommend checking out the official websites or fan wikis dedicated to the series.