I am posting this here as well as in the thread to make sure you see it.
Well, if it says that and doesn't ask if you want to read it, chances are you are playing Diamond or Pearl, in which case you don't need Manaphy. You only need Manaphy in Platinum. If you are playing Platinum, you're talking to the wrong book then, because no matter how early in the game you are at, it will show you a picture of Manapy and add it to your dex. The book is on the desk right behind Backlot or whatever in his mansion on the table.