Engine > Book Options
Use this dialog box to determine how the engine uses the book.
Use book
Determines whether the engine uses the book at all.
Minimum games
Tells the engine how many games must be available for a move for it to be played. If you enter 2 then the engine is allowed to play the move only if the position after the move has occurred in 2 games or more.
Variety of play
Determines which moves the engine will choose to play: only the ones with the highest statistical values, or the more seldom moves as well (slider right = varied). If the slider is on the left then the engine only plays the move with the most number of games. If the slider is on the right then the engine chooses between all book moves. The chance a book move is played depends in the number of games, i.e. the moves with the highest number of moves have the highest chance to be played by the engine.
Database
Choose the database the engine has to use.
The way the engine plays the opening depends on the games in the database. Do you want to play with the while color against Sijbrands? Then make a database with all games of Sijbrands playing with black. Do you want to play with the black color against Sijbrands? Then make a database with all games of Sijbrands playing with white. Do you want to train a specific position? Then search all games with that position and make a database with only these games.