He certainly seems to be a polarizing force ... as it often seems with anyone with a strong opinion or creative point of view. (Monk, Trane, Ayler, Cecil) As can be seen here, a great many don't seem to enjoy his work, while others believe it is the work of genius. As you will note below, I tend toward the later.
My wife and I have enjoyed his work immensely and been most fortunate to have been living in NYC in the past six+ years and seen: the Lincoln Center staging of Passion and the Broadway revival productions of Assassins, Pacific Overtures, Sweeney Todd, Company, Sunday in the Park with George, A Little Night Music, along with Gypsy and West Side Story.
Musically, the only things I have enjoyed anywhere nearly as much in that time were Spring Awakening and Light in the Piazza.
There certainly was a greater simplicity to many earlier lyricists' work. Much was even nonsensical. I am looking forward toward reading the book. Having heard him speak on such topics, I wonder if that was the point of reference. He seems to take great pride on his construction of real intelligent dialog - words within his music.