In One's Book Meaning

Example: In one's opinion.
1973, QST, Volume 57, Issue 2, page 87,
  Is this "the field?" Not in our book, it isn't.
1975 Feb 8, Kevin O'Donohue, Stan Clark, Brian McClenaughan, Frank Jeffcoat, Four Broadcasters Compare U.S. Radio with Australian Radio - The Knockout Blow, in Billboard, page A-7,
  [Jeffcoat:] I'll qualify that in a moment, but in my book I think when it comes to sheer professionalism, there's nothing quite like an American broadcaster.
1978, William James, Frederick Burkhardt, Fredson Bowers, Ignas K. Skrupskelis, Essays in Philosophy, page 66,
  My solution, or rather Stumpf's (for in my book I am but the humble follower of the eminent Munich psychologist), was to take neither of these objectionable alternatives, […] .
2007, Ralph A. Gessner, Deep in My Heart, page 105,
  That's taking things way too far in my book.
Used other than as an idiom: see in,‎ one's,‎ book.