The Chronicles of Lucius Leffing by Joseph Payne Brennan (1977)
There have been many occult detectives in literature: Algernon Blackwood's John Silence, William Hope Hodgson's Carnacki, Kate and Hesketh Pritchard's Flaxman Low, Seabury Quinn's Jules de Grandin, J. U. Giesy's Semi-Dual, Sax Rohmer's Morris Klaw, Dion Fortune's Dr. Taverner, Manly Wade Wellman's John Thunstone, Margery Lawrence's Miles Pennoyer, Rick Kennett's Ernie Pine, James Herbert's David Ash...I could go on. One of my favorites is Joseph Payne Brennan's understated Lucius Leffing of 7 Autumn Lane, New Haven.
It's hard to explain why. The vast majority of his thirty-nine recorded cases have absolutely nothing to do with the occult. Leffing himself is a gentile antiquarian with a taste for sarsaparilla, root beer, and good cognac (no, not mixed together, heaven forfend!). His investigative technique seems to be to ask a few innocuous questions and then to sit for a day (or two, or three) and mull things over in his mind. His conclusions seem conveniently strained an are occasionally wrong. He works out of his home and has a hard time eking out a living; he often works pro bono with the New Haven homicide department. Leffing's Watson is Brennan himself; the author injects enough of himself into the stories to make them more interesting. Brennan -- as Watson -- can be brilliantly intuitive or maddingly obtuse, depending on the story. Leffing's adventures are leisurely and often undramatic. Action is seldom called for. Vital clues are often mentioned only after the case is solved. Yet there is something about Leffing and Brennan's writing that draws me.
A librarian at Yale University for over 40 years, Brennan began publishing in 1940 with a poem. He eventually wrote well over a thousand poems and published as number of poetry collections. He also created and edited the small poetry Journal ESSENCE which produced 47 issues over a period of 28 years. His first prose publication was a western short story; he went on to write over two dozen westerns for the pulps. Brennan began writing horror fiction in the early fifties. A number of his stories in that field are recognized classics. He created his own publishing house, Macabre Press, and edited the fiction magazine MACABRE for 23 issues.
The Chronicles of Lucius Leffing contains eight stories, including several from Alfred Hitchcock's Mystery Magazine and Mike Shayne's Mystery Magazine, with only the final being occult in nature. In his introduction to the book, Frank Belknap Long quotes editor Leo Margulies on one of Brennan's stories, "They seldom write stories like this any more, Frank. Leisurely and scholarly in style and utterly splendid from beginning to end." Despite the faults mentioned above I found all of the stories in this book to be "utterly splendid from beginning to end." In particular, I enjoyed "Mem'ries," in which Brennan relates to Leffing some of problems he has with his poetry magazine ESSENCE, never realizing the dangers of rejecting a manuscript.
To my knowledge, all of the Leffing stories have been published in these three collections and one short novel:
The Casebook of Lucius Leffing (1973)
The Chronicles of Lucius Leffing (1977)
The Adventures of Lucius Leffing (1990)
Act of Providence (with Donald M. Grant, 1979)
(Leffing also made a cameo appearance in the story "In the Very Stones" which was reprinted in his collection Scream at Midnight (1963).)
The four Leffing books were all published in limited print runs and are difficult to find inexpensively. I read all four volumes over the years via interlibrary loan. You may find it worth your while to do the same.