Gergely Hubai has a regular, monthly column on the online FILM SCORE MONTHLY which includes not only material that he could not fit in his book, but new stories about composers and their unused scores.
The book is a great read and one that I can go back and reread for its well-researched sections and interviews with the composers themselves.
Please not that Hubai has had a hand in obtaining the release of two unreleased scores on Perseverance Records: Philip Lambro's Los Angeles, 1937, the unreleased score to CHINATOWN, and John Corigliano's score MUSIC FROM THE EDGE (guess what Mel Gibson film that this is from?).