I have what I think is latest version copyright 2011 with a light blue cover. I believe the earlier version has the same problems/solutions and different cover. There may be some errata as well. If you have earlier version, be aware of the following.
... they state "new look, same questions" or something like that and "The questions and solutions are very similar in the current edition of the POWER book and the edition with ISBN 978-1-932613-38-4 on the back cover. Call customer service at 800-250-3196 before ordering if you have any questions about your edition of the book"