 Radford compares these investigations to a crime scene investigating where there exists "a positive correlation between the quality of the available evidence and solving the mystery".Radford states he has a "high bar for what I am willing to concede is 'unexplained' or truly mysterious".Paranormal researcher Brian D. Parsons in a review for "Investigating Ghosts" states that he wishes a book of this quality existed back when he (Parsons) was starting out.