Jansen is a graduate of the University of Amsterdam, his doctorate in Arabic is from the University of Leiden. He has worked in Egypt, where he was the Director of the Dutch Research Institute in Cairo. From 1983 he was an associate professor of Arabic and Islamic studies at Leiden University. Up to 2008, he was Houtsma Professor of Modern Islamic Thought at the University of Utrecht.
He is a regular newspaper columnist and frequent media commentator. He was a principal witness in the trial of Geert Wilders, during which a judge approached him during a dinner party and allegedly tried to convince him that the trial was justified. As a result, the judges were substituted and a retrial was ordered. The judge who was alleged to have attempted to influence him, Tom Schalken, subsequently retired from the bench.
Furthermore, he is currently placed in the electable number 4 candidate position of the Islam critic PVV list of Geert Wilders for the upcoming elections for Dutch representatives to the European Parliament.
He was an expert witness on the Koran and Shariah in the trial in Birmingham Magistrates Court (Crown vs Timothy Martin Burton) on 8 April 2014, which came to be known as the Birmingham Taqiyya Trial. (Mr Burton was subsequently found not guilty of Racially Aggravated Harassment.)
His website, partially in English - http://www.arabistjansen.nl - contains a list of publications and a CV.
Books in Dutch:
- Inleiding tot de Islam (1987)
- De Koran uit het Arabisch Vertaald door Prof. dr. J.H. Kramers (1992) (edited by Asad Jaber & Johannes J.G.Jansen)
- Nieuwe Inleiding tot de Islam (1998)
- Het Nut van God (2001)
- God heeft gezegd: terreur, tolerantie en de onvoltooide modernisering van de islam (2003)
- De radicaal-islamitische ideologie: Van Ibn Taymiyya tot Osama ben Laden, Oratie Universiteit van Utrecht, 3 februari 2004
- Islam: een hoorcollege over de islamitische godsdienst en cultuur (2005, audio-cd)
- De historische Mohammed: de Mekkaanse verhalen (2005)
- De historische Mohammed: de verhalen uit Medina (2007)
- Bombrieven (2008, correspondence with Abdul-Jabbar van de Ven)
- Islam voor varkens, apen, ezels en andere beesten (2008)
- Zelf Koran lezen (2008)
- Eindstrijd, edited by Jansen & Snel (2009)
Books in English (Many other titles are not yet available in English):
- The Interpretation of the Koran in Modern Egypt (Leiden: E.J. Brill, 1974)
- The Neglected Duty: The Creed of Sadat’s Assassins and Islamic Resurgence in the Middle East (New York: Macmillan, 1986)
- The Dual Nature of Islamic Fundamentalism (London: Hurst & Company, 1997) ppls