Probably dummies. They're all covering where the book they'd be holding would be. The probably took it before with dummy books/no books, then got a few copies of those, and took the real picture. At least that's my guess.
The real question is, do the books they are holding in the picture have them holding those books on the books cover... and do those books have them holding the book.... oh god where does it end!!!!
Recursion is the word you're looking for.
http://www.atcincometax.com/wp-content/uploads/2013/03/College-Students-Can-Get-Money-Today-From-The-IRS-960x1024.jpg