Hammer has written four books in Swedish and one monograph Claiming Knowledge: Strategies of Epistemology from Theosophy to the New Age (2001) in English. This volume, which was also Hammer's doctoral dissertation in 2000 at Lund University, investigates the rhetorical strategies of legitimization of a number of related new religious movements. Hammer is also editor of several books, including Polemical Encounters (with Kocku von Stuckrad, Brill 2007), The Invention of Sacred Tradition (with James R. Lewis, Cambridge UP 2007), Alternative Christs (Cambridge UP 2009), Cambridge Companion to New Religious Movements (with Mikael Rothstein, Cambridge UP 2012), and Western Esotericism in Scandinavia (with Henrik Bogdan, Brill 2016). He was from 2009 to 2016 one of two executive editors of the journal Numen.
In 2002 the title of årets folkbildare in Sweden was bestowed on Hammer (an honor which could best be translated as "Public educator of the year"), by the society Föreningen Vetenskap och Folkbildning "for his balanced and pedagogical books about the history of new religions and the causes behind people's beliefs in pseudoscience."
- årets folkbildare 2002
- LIBRIS record for Olav Hammer
- "Numen: International Review for the History of Religions". Brill Publishers. Retrieved September 28, 2014.