Read more about it: Archduke Otto

Gordon Brook-Shepherd's Uncrowned Emperor is the only English-language biography of Archduke Otto of Austria.   This book was published in the US and in the United Kingdom.

http://www.amazon.com/Uncrowned-Emperor-Life-Times-Habsburg/dp/1852855495/ref=sr_1_2?s=books&ie=UTF8&qid=1297186235&sr=1-2.

Brook-Shepherd is also the author of The Last Empress, a biography of Empress Zita, consort of Karl I, and mother of Archduke Otto.

An authorized biography of Archduke Otto, Otto von Habsburg. Die autorisierte Biografie, was published by Amalthea-Verlag in 2007.  This book has not been translated into English.   The author is Eva Demmerle, who held various positions in the European Parliament, and currently works as Archduke Otto's press spokeswoman.