Extreme Pokémon: The Guide for the Ultimate Fan by Michael Teitelbaum is a handbook that was published in July 2000. It contains some basic information on Generation I and, more specifically, information on characters and events occurring in the Orange Islands story arc of the anime. The book also contains the only official map of the Orange Archipelago.
On page 7, there is a list of the Kanto Gym Leaders. The image of the Badge Sabrina gives out, the Marsh Badge, and the Badge Koga gives out, the Soul Badge, are switched.
On page 32, when listing Pidgeot's attacks, one of them is "Wing".
On page 33, a section called Mime's The Word states that Delia rescued her Mr. Mime from a circus where it was being treated harshly. In reality, hers was a wildMr. Mime which she mistook for Ash. The Mr. Mime in question actually belonged to Stella who eventually worked out her differences with her Mr. Mime.
On page 90, a question asks The S.S. Anne is a boat docked in Vermilion City. True or False? The answer on page 105 does not make sense saying False, the name of the boat is the S.S. Anne.
This is actually corrected in the Canadian French version. In this translation, the question asks if the name of the ship is the "S.S. Banane".
On page 104, the answers are given for You Pick the Winner! Battle #3 says Pikachu will win in a battle against Golem because "Water-Type Pokémon have the advantage over Rock Types." This may be referring to Surfing Pikachu, as Surf is a Water-type move.