[AMF]

AS mentioned below, it's a strip to set off the detectors at the doors to the building where the book lives. Also used on CDs and other items of similar nature to prevent them from being stolen.

Of course, you coudl take the other view: have a $20 US bill? Hold it up to the light. See that small strip running through it? Those strips and the strips in the books are the same, and are tied into the GPS tracking system so that THEY can track what money you spend and what books you read at any given time. Furthermore, if you've ever been under anesthesia anytime in the past ten years the doctors inserted into your body itself one of those little things, so now they track you too.

Just kidding.

heh.