Holly,
An x-pen is an option or, if not for you, then I'd certainly move all the books out of puppy's reach!
I also think the suggestion to walk him before you leave is a good one.
In addition, I'd leave stuffed Kongs for him. They can entertain themselves for long periods of time with those. I freeze Joey's so that it takes him even longer to work the food out.
I'd also do work with him about making him more comfortable with your leaving as described in this article (just ignore the parts that don't apply):
http://www.clickersolutions.com/articles/2002/sa.htm
Good luck!