He is the author of the book Führer Ex: Memoirs of a Former Neo-Nazi (with Tom Reiss), also made into a movie directed by Winfried Bonengel, which has been translated into several languages.
His acrimonious departure from the neo-Nazi community and the publication of his books, Die Abrechnung: Ein Neonazi steigt aus written with Winfried Bonengel in 1993 and Führer Ex written with Tom Reiss in 1996, caused his former comrades to send him a letter bomb disguised as a book, which package was opened by his mother, without however sustaining injury.
Hasselbach then confessed his accumulated knowledge about the neo-Nazi community to the German Federal Criminal Police Office.
After 1995 he traveled quite often to the United States where he began to work as a journalist in the immediate aftermath of the Oklahoma City bombing, focusing on local extreme right-wing terrorism.
Having finished his second book Die Bedrohung - mein Leben nach dem Ausstieg (The threat - my life after the dropout) in 1996, Hasselbach lived for some time in the U.S. and the U.K. and campaigned publicly for the abolition of the death penalty and had numerous articles published in the news media on that topic.