Make Book Meaning

(idiomatic) To be very confident.

Example: 1954, "Into the Stretch," Time, 30 Aug.:
  In the American League, front-running Cleveland was an odds-on favorite with the men who make book on baseball.
1909, Rex Ellingwood Beach, The Silver Horde, ch. 25:
  "Oh, you can make book that she didn't start no love-making. She ain't the kind to curl up in a man's ear and whisper."