Not sure if you got "The Black Camel" #4 reprint off the local over priced big box book store shelf. Previously I got #1 & #2, but book reprint #3 was missing. I think they are reprinting all 6 Biggers stories.
Like you, I am enjoying the read (just made it up to Sheila getting stabbed), and have visions of the movie floating around in my head.
If I remember correctly, the character in the movie (Jessop) was also Bela's most able assistant in Dracula.