Welcome to my favorite Genesis album (and I do like Genesis). This title song of the album is actually my second favorite of the album (the first will come later).
I was in college at CSU Sacramento when I really fell in love with this album. It was an odd experience – I had a fantasy fiction class in college and we were reading Lilith: A Romance by George MacDonald. It was a bit of a dense read but the lyrics from this album tie in to the point I wondered how influenced Peter Gabriel might have been by this book.
It was five minutes ago I found the answer on Google Books from a book called Prog Rock FAQ by Will Romano:
AHA! It was kismet that the album and the book came to me at the same time.