The Letter Of Marque by Patrick O'Brian

Captain Jack Aubrey, a brilliant and experienced officer, has been struck off the list of post captains for a crime he did not commit. Old friend Stephen Maturin, of British intelligence, gets Aubrey to help him in a desperate mission against the French which, if successful, may redeem Aubrey from the private hell of his disgrace. "A splendid saga".--Los Angeles Times Book Review.