Mark Twain's Vintage 'Visions of Darkness'

Actually, this is an article written two years previous to Mr. Clemens death(1908) and includes a picture of him. I found the article in "Mr. Clemens and Mark Twain" by Justin Kaplan, who published the book in 1966.

"Mr. Clemens and Mark Twain" won a Pulitzer Prize and the National Book award in 1967, and has what i believe to be a computer generated copy of Clemens signature, being as it was published fifty-eight years after his death.

What i really want to know is how much the article would be worth now, and how much if I kept it for a bit.