Book - chess glossary
Book
Definition
In chess, “book” refers to established, documented theory—most often in the opening phase. A “book line” is a sequence of moves that is widely accepted as standard; a “book move” is a theoretically approved move within such lines. By extension, “book” can also describe theoretically known endgame results, such as a Book draw or Book win.
How it’s used in chess
Players and commentators say things like “still in book” when the game follows known Theory; “out of book” when someone deviates and must think independently; and “booked up” when a player has studied a line deeply. Engines and databases also use an “opening book” to select early moves without calculation.
Strategic and historical significance
Knowing the book helps you reach good positions efficiently, save time on the clock, and steer the game toward structures you understand. Historically, “book” came from printed opening manuals and anthologies (later systematized by ECO codes A00–E99). With databases and engines, book knowledge expanded rapidly; today, elite preparation often goes 20–30 moves deep in sharp openings. “Book” also codifies many endgames: certain positions are known to be theoretical wins or draws with perfect play.
Examples of “book” lines
- Ruy Lopez, Closed Main Line (a classic “in-book” sequence for many moves):
- Sicilian Najdorf, main tabiya (deep, heavily analyzed “book” battleground): ECO B90–B99
- Endgame example of a “book draw”: bishop plus wrong rook pawn vs. king, or rook vs. rook with the Philidor setup—standard theoretical results that every endgame student learns.
Famous games and anecdotes
- Fischer vs. Spassky, World Championship 1972 (Game 6): A Ruy Lopez masterpiece where both sides followed deep book before Fischer’s instructive middlegame squeeze.
- Kramnik vs. Kasparov, World Championship 2000: The Berlin Defense became top-tier “book,” reshaping 1. e4 e5 opening theory for decades.
- Kasparov vs. Deep Blue, 1997: The machine relied on a curated opening book; human and engine “book prep” famously battled before fresh positions arose.
Practical tips for using “book”
- Build an opening repertoire around structures you like, not just the engine’s first line. Seek lines with good Practical chances.
- Study critical sidelines too; many wins come when opponents force you “out of book.”
- Connect openings to typical middlegame plans and endgames; don’t rely on rote memorization alone.
- Know key theoretical endgames—common Book draw and Book win patterns save points.
Related concepts
- Book move: a standard, approved theoretical move
- Theory and “main line” vs. sidelines
- Prepared variation, Home prep, Novelty/TN (a new idea that departs from book)
- Endgame theory: Book draw and Book win classics like the Lucena and Philidor positions
Interesting facts
- “Book” started as literal books (e.g., ECO, Informant); today it often means databases and engine-assisted files.
- Engines use opening books to save time and avoid early evaluation quirks; similarly, humans conserve clock time by staying “in book.”
- Leaving book at the right moment is an art: strong players choose deviations that maximize discomfort for an opponent’s preparation.
Quick glossary
- In book: Following established theory.
- Out of book: The first new move or deviation; independent play begins.
- Book line: A well-known sequence accepted by theory.
- Book eval: The theoretical assessment of a line (e.g., “slight edge for White”).