This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff on-line! See this thread for details.
If you want to be thorough, I'd recommend learning about EJBs since it will benefit you when you later study Java web services.
A good book on web services is "Java Web Services Up and Running" by Martin Kalin.