"Kingliveson.abk is a huge chess opening book for free chess graphical user interface (GUI) Arena for chess engines.
The book is composed of 75 percent engine games and 25 percent human (Grandmaster) games. The minimum engine ELO rating is 2700. There are no drawn games used, and all games are long games—no blitz. The book has been fine tuned and tested against freely available books."
50mb = 625mb decompressed