My girlfriend is not a native English speaker, so sometimes she has questions about expressions for which I do not know the origins.
This one, in particular, got me curious:
"I have this book" vs. "I have a copy of this book"
About music, you don't say:
"I have a copy of this song" but "I have this song"
Similarly, I never hear:
"I have a copy of this DVD" but "I have this DVD"
However, for books, I have commonly heard, and used myself for no special reason: "I have a copy of this book"
Is there a reason we sometimes refer to a book as a copy of the book?
But
Best Answer
Actually, people do say they have copies of other things, it's just that books are the most common:
It's also very common to say some song sold N million copies.
I have X usually means the same thing as I have a copy of X, except when it means I have the original X.