This is the book title that Locke is shaking upside down in the latest episode. The story is pretty interesting and was eventually turned into a Twilight Zone.
The basics are this (as I recall - I read the story years ago):
Man is believed to be a Confederate soldier in the Civil War. He is captured and taken to Owl Creek Bridge. Union soldiers wrap a noose around his neck and push him over the side to hang him. Only problem is that the rope breaks and the man falls the ground below. He manages to survive the fall and dashes off to the safety of his home to be reunited with his wife. Happy ending - The End.
Well, actually the end is him swinging from the bridge with the rope around his neck. The rope never broke. The entire story took place in a matter of seconds and was completely in his mind.
For those interested you can read the short story HERE.
Now the question is … did the writers throw this in here as a clue or red herring?