Some people say that writing the arrangements on his first album, Matthew and Son, is what drove him crazy. There were some great songs on this effort, such as "Hummingbird," "Here Comes My Baby," (later covered into a hit by the Tremolos) and my favorite, "Bring Another Bottle Baby."
His next album, New Masters, had the song the First Cut Is the Deepest, which was about all there was there.
The album that put him in the limelight for the hippies was Tea for the Tillerman in 1970. It contained "Wild World," "Longer Boats," and "Father & Son."
He seems to be happier as a Muslim; more power to him.