Complex sentence: Despite her apparently premature death he never lost faith in her divine mission or the possibility that she would reappear, and wrote a book in her defense: "An answer to the world etc." (London, 1806).
Split into simpler sentences: Despite her apparently premature death he never lost faith in her divine mission or the possibility that she would reappear. He also wrote a book a book in her defense: "An answer to the world etc." (London, 1806).