George III had at least five periods of overt mental illness, the first in 1765 at the age of twenty-seven, the last during the final decade of his life, from the age of seventy-six (1810 to 1820). Guttmacher has written a detailed psychiatric biography based upon the works of historians and records of contemporaries of George III, and upon unpublished letters of the King and his intimates. He has also used other little known source material found principally in the Royal Archives of Windsor Castle. The result is an informative and for the most part interesting, though occasionally obscure and repetitious, study of a man whom most of our textbooks misrepresent and most Americans misunderstand.