This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
I don't think Apress has posted any sample chapters, yet. However, you can get a sample chapter from the previous edition, Pro EJB 3 at http://www.apress.com/book/downloadfile/2807. That will give you a feel for the writing style and let you know if it fits with the way that you like to get information. Pro JPA 2 just includes updated and additional content than what is in the previous edition.