Cale is mentioned in a lot of books. A short list of interesting volumes:
Lit Riffs (Ed. Matthew Miele)
Writers "cover" songs they love. Contains the short story Dying On The Vine by Elissa Shappell.
Nico - Songs They Never Play On The Radio (James Young)
Written by her former keyboard player. Cale as a druggy producer of the Camera Obscura album and sharing the bill on a Japanese tour.
Punk! - An A-Z (Barry Lazell)
Forword by John Cale.
Lou Reed - Growing Up In Public (Peter Doggett)
The Velvets, Songs For Drella.
Lou Reed - The Biography (Victor Bockris)
The Velvets, Songs For Drella, the reunion tour.
Patti Smith (Victor Bockris)
Producing the Horses album and supporting the 1976 tour.
There's Something About Jonathan - Jonathan Richman and the Modern Lovers (Tim Mitchell)
The aborted Modern Lovers album sessions.