The value of the first move is 40 rating points (1/5 of a Pawn). Going back to the table from 'Chess Ratings' (rating expectancies vs. differences), a difference of 40 rating points gives the higher rated player a little less than a 0.56 chance of winning the game. This means a 56% expected score for White, and a 44% expected score for Black, which is close to the result derived from databases of historical master-level games.
How does that square with the 'Black Is OK' books by GM Andras Adorjan? Here are the publication dates and titles of the three books in the series:-
- 1988: 'Black Is OK!'
- 2004: 'Black Is Still OK!'
- 2005: 'Black Is OK Forever!'
I once reviewed the last title, Black Is OK Forever!, and have since acquired the first two titles, so I'm ready to roll.