The excerpt below, from Henry Howard Harper's Booklovers, Bibliomaniacs, and Book Clubs (1904), is an early attempt at explaining what Joli Jensen, in 1990, called “fandom as pathology." I’m not sure the author succeeds in moving beyond the disease metaphors! Good point, at the end, though, about how some people, more than others, are apt to be labelled maniacal.
"It should be remembered that one possessing a fondness of books is not necessarily a bibliomaniac. There is as much difference between the inclinations and taste of a bibliophile and a bibliomaniac as between a slight cold and the advanced stages of consumption. Some one has said that 'to call a bibliophile a bibliomaniac is to conduct a lover, languishing for his maiden’s smile, to an asylum for the demented, and to shut him up in the ward for the incurables.' Bilbio relates to books, and mania is synonymous with madness, insanity, violent derangement, mental aberration, etc. A bibliomaniac, therefore, might properly be called an insane or crazy bibliophile. It is, however, a harmless insanity, and even in its worst stages it injures no one. Rational treatment may cure a bibliomaniac and bring him (or her) back into the congenial folds of bibliophilism, unless, perchance, the victim has passed beyond the curative stages into the vast and dreamy realms of extra-illustrating, or 'grangerizing.' People usually have a horror of insane persons, and one might well beware of indulging a taste for books, if there were any reasonable probability that this would lead to mental derangement. There could be furniture-maniacs, rug-maniacs, and china-maniacs, but people do not generally hesitate to purchase furniture, rugs, and china for fear of going crazy on the subject, and no more reason is there why rational persons should hesitate to make a collection of good books for a library, for fear of being called bibliomaniacs. In Sesame and Lilies Ruskin says: 'If a man spends lavishly on his library, you call him mad—a bibliomaniac. But you never call one a horse-maniac, though men ruin themselves every day by their horses, and you do not hear of people ruining themselves by their books.'"