For whatever reason, I recently read 3 out-of-copyright ebooks on the Project Gutenberg website, all fictions about ghosts. They all took different approaches to the subject:
A Master of Mysteries by Robert Eustace and L. T. Meade – PG ebook 22278. One reviewer described this as being at the “Scooby-Doo” end of the spectrum because all of the storys have a natural cause (often malicious). John Bell investigates and solves. My favorite of all of these is “The mystery of the Felwyn Tunnel” – you may feel yourself inching close to the answer like I did. I got the concept of the solution right, but the details wrong. Has strong similarities to Charles Dickens’ “The Signal-Man” (story 3 here).
Carnacki, the Ghost Finder by William Hope Hodgson – PG ebook 10832. In between John Bell and Flaxman Low is Carnacki: some of what he turns up are real ghosts (he is more specific than that) and others are not. At least 2 are both.
Flaxman Low, Occult Psychologist by E. and H. Heron – PGA ebook 0605881. On the other end, all of Flaxman Low’s storys involve “psychical” beings. Worth noting is that he has a systematic taxonomy sort of thing for these. That is, there is variation of types of spirits, what causes them, how to deal with them. This is similar to what Elliott O’Donnell did/tried to do.