Book of Taiyou is a Normal Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Book of Taiyou is Unlimited.
YGOPRODeck lists Book of Taiyou for these formats: GOAT, OCG GOAT, Duel Links, Common Charity, Edison, Speed Duel, TCG, OCG, Master Duel.
Book of Taiyou belongs to the Book of archetype—use that tag when searching for engine pieces and tech options.
A listed print of Book of Taiyou appears in Champion Pack: Game Two (CP02-EN017) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Book of Taiyou is about $0.10 on TCGPlayer (prices change frequently).
