"Spellbook Magician of Prophecy" and "Spellbook of Secrets".
Several "Spellbook" cards are based on mystical tomes and books from history.
Most of the cards in this archetype are Spell Cards. The exceptions are "Hidden Spellbook" and "Spellbook Magician of Prophecy". As such, numerous support cards like "Spellbook of Life" cannot use them for their effects, nor can they help you get or use them. "Prophecy" cards usually specify a "Spellbook" Spell Card in which they are also excluded. However "Spellbook of Secrets" is an exception, as it does not specify a Spell Card specifically, so it can still search them out.
Due to these cards searching each other out, they can be useful in Deck Thinning. Additionally, due to their effects benefiting Spellcaster-Type monsters, these cards can easily be used in a Spell Counter-based Deck for massive amounts of Spell Counters to be created. "Hidden Spellbook" can be used in this case to recycle those cards for future use. Also cards such as Spellbook of Judgment can be used to replenish your hand full of spellbook cards after you have used many during that turn.
Spellbooks aren't without flaws, as there are many ways to shut a Spellbook deck down. The first and most obvious way to shut this deck is with cards that negate spells/ negate and destroy spells/ allow limited activation of spells such as "Horus the Black Flame Dragon LV8" , "Dark Bribe" , "Spell Shield Type-8" , "Spell Canceller" , "Great Shogun Shien" , etc. Next is the fact that almost all of the Spellbook spells, (except for "Spellbook of Wisdom" can only be activated once per turn, so if you activate any Spellbook spell, except for Wisdom, and it is negated, you cannot activate any more copies of that said Spellbook spell again in the same turn, rendering all other copies of the said Spellbook card in your hand useless during that same turn. Another way to stop Spellbooks is with cards that restrict searches, like "Thunder King Rai-Oh" and Droll and Lock Bird" can also prevent a Spellbook user from getting other Spellbooks via searches. "Prohibition" can also stop the reuse of one of your spell books, limiting you only slightly. "Deck Devastation Virus" can send all of your Spellbook spells in your hand and on the field, to the graveyard and prevent you from drawing any other spells, be it a Spellbook spell or any other spell. "Mind Crush" can also be used to counter this deck to an extent, and can send a newly added Spellbook in your hand to the grave. And while some "Prophecy" monsters can search for Spellbooks/ add them to the deck and/or hand, cards that negate effects like "Divine Wrath" , "Effect Veiler" , "Skill Drain", etc., can easily prevent their abilities. "Skull Invitation" can rack up damage on a Spellbook deck, due to the amount of spells being activated per turn and sent to the graveyard, though it will take away a good 1200LP to 1500LP if the player doesn't care about the loss of lifepoints.