This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
German is my mother tongue, so i can't recommend a book. But check out the German courses of Goethe-Institut.
Maybe there's one next to you.
One advantage is that their certifications are officially recognised.
subject: Books for Spanish and German languages grammar