The above are the default settings, play random for diversification.
. [Book Use = best] plays the move the highest percentage.
. [Book Score = on] plays the move with the highest Stockfish score.
. [Book Learner = on] plays the move with the highest learn score.
. [Book Extension = on] makes use of the big book10 | book20 | book25 opening books when
the main book fails to produce.