Harrison's book, first published some 20 years ago, is now seriously out of date. More recent research has shown much of his material to be ineptly researched, misleading or downright wrong and it's a great shame no effort has been made to correct the numerous errors identified by careful reinvestigation of some of his leading cases. Those interested in SHC would do much better to check out more recent books such as those by John Heymer, Jenny Randles and Peter Hough, or Larry E Arnold (if you want a generally 'pro' point of view), or Joe Nickell, for the skeptical perspective.