Book Move - Chess Glossary
Book Move
Definition
A book move is any chess move or sequence of moves that has been thoroughly analyzed and documented in opening reference works—traditionally printed “opening books,” and today also large electronic databases (“opening books” in engine GUIs or cloud services). When a player follows established opening theory rather than calculating the position from scratch, they are said to be “in the book.” Leaving these known paths is called “going out of book.”
How It Is Used in Chess
During the opening phase, strong players consult their preparation—commonly stored as an engine-checked repertoire—to decide whether the current position has appeared before and what the vetted continuations are. In practical play the term surfaces in several ways:
- Pre-game preparation: “My opponent plays the Najdorf; I memorized 20 book moves.”
- Post-game analysis: “We were still in the book after 14…e5, then he deviated.”
- Time-management commentary: “She spent only a minute on the first 12 moves—clearly book moves for her.”
Strategic Significance
Remaining in the book carries several advantages:
- Efficiency: Saves clock time early in the game.
- Reliability: Builds on positions vetted by generations of masters and engines.
- Psychological edge: Taking an opponent out of their preparation can induce uncertainty or time pressure.
- Theoretical battles: Top players often test novelties (new moves) aimed at refuting or improving upon accepted book lines.
Historical Background
The very first printed opening manuals—Gioachino Greco’s 17th-century
manuscripts, Bilguer & von der Lasa’s Handbuch des Schachspiels
(1843), and later Reuben Fine’s Ideas Behind the Chess Openings
(1943)—codified what was then known theory. With computers, the bulk of
“book” expanded exponentially. Today’s engines carry built-in polyglot or
proprietary books with millions of games, and professional players compile
personal trees where each move is tagged book, checked,
or novelty.
Examples
- Sicilian Najdorf: 1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6. All five moves for each side are among the most time-honored book moves in chess.
- Bobby Fischer’s “Poisoned Pawn” preparation (Fischer–Larsen, Candidates 1971): After 6. Bg5 e6 7. f4 Qb6 8. Qd2 Qxb2, Fischer was still in book—Larsen was not.
- Modern Engine Prep: In the 2018 Carlsen–Caruana World Championship, Game 1 followed book theory of the Rossolimo Sicilian for 14 moves before Caruana introduced 14…b5.
Interesting Facts & Anecdotes
- Garry Kasparov reportedly memorized more than 10,000 book positions at his peak.
- “Out of book on move one” became a meme after Magnus Carlsen’s surprise 1. f3? in a blitz game—intentionally untheoretical.
- The shortest grandmaster game to leave book is arguably Nakamura–Aronian, Wijk aan Zee 2011: Aronian’s novelty 6…Bf5 took the world’s databases by surprise and immediately put Nakamura on his own.
- Engine creators often ship a “narrow” book to encourage diversity in computer tournaments, preventing endless mirror repetitions of top theoretical lines.
Common Phrases
• “Book up” = study openings.
• “Book draw” = a well-known theoretical draw, often in endgames.
• “Book trap” = a tactical pitfall lying in wait for the unprepared, e.g.,
the Elephant Trap in the Queen’s Gambit Declined.