Actually, it's a bookmark!
The entire image is of an opened Moleskine sketchbook.
I love these things. They make sketching in them very easy as the book seems to naturally stay open flat.

Legend has it that this is the same book Picasso, Matisse and Hemingway used. I recommend this Wikipedia entry about the Moleskine for more information about the greatest thing since slice bread.

The nice man over at pixelpressicons.com created some cool Moleskine icons for the Mac.