The Black Falcon by Walter B. Gibson (no relation, unfortunately) writing as Maxwell Grant is not a horror novel. It's a classic "crime mastermind" thriller, with elements of whodunit and suspense woven in. The thing that makes it appropriate fare for this space is the lead character - The Shadow, who is basically Halloween incarnate, a dark figure (or "personage," to use one of Gibson's favored word motifs) who stalks New York City by night fighting crime through mysterious means. He dresses up in a black slouch hat and black cloak, only he's not doing it to acquire candy from neighbors - his face was hideously scarred in the war, apparently so much so that when anyone looks at his undisguised face they go into palpitations of shock and terror.
That's what happens to the titular Black Falcon, who is a criminal genius whose modus operandi is briefly thus: He kidnaps wealthy businessmen in between taunting letters to the police (signed with a black falcon's feather), vaguely demands ransom but never attempts to collect, and holds his victims in his lair out in the suburbs. When he feels the need to appear publicly, he wears a black mask over this eyes so as not to be recognized as his true identity, which I will not reveal (I've been keeping track of Gone Girl reviews so I know how angry everybody gets about spoilers), except to say that he's one of the rich businessmen who is ostensibly threatened by the Falcon's schemes.
It's not the most well-defined criminal plot in the history of pulp fiction, but the reader does get the sense that The Black Falcon does stand nearly eye-to-eye with The Shadow in the scheming department, especially after he kidnaps wealthy Lamont Cranston, whom he believes to be the secret identity of The Shadow - the truth, as it always is, is more complicated than that, but I won't reveal that either - just don't believe what the movies tell you.
To use a favorite Matt Lynch-ism, there are some threads here that never get tugged over the course of 60 pages, like the fact that The Shadow and The Black Falcon are distorted mirror images of one another, down to the fact that they each favor a mocking, sardonic demeanor when in character. Or the economic implications of a criminal targeting wealthy businessmen through his ability to move comfortably in their social circles - an alternate title for this story, written in 2014, might be Murder By Privilege. Like with most hero pulps, though, you pretty much have to use your imagination and tug on these threads yourself. Which, of course, is a pleasure.