Hjort is also a rock historian and researcher. In 2000, together with American Doug Hinman, he published Jeff's Book, an acclaimed annotated chronology of Jeff Beck's career, followed first in 2007 by Strange Brew: Eric Clapton and the British Blues Boom 1965–1970 and then by So You Want To Be A Rock'n Roll Star: The Byrds Day-by-Day 1965–1973.
Hjort is also a rock music historian and researcher. In 2000, he co-authored Jeff's Book with Doug Hinman, an acclaimed detailed account of Jeff Beck's career, which was followed by Strange Brew: Eric Clapton and the British Blues Boom 1965–1970 in 2007 and So You Want To Be A Rock'n Roll Star: The Byrds Day-by-Day 1965–1973.