A medium sized dictionary is quite useful, otherwise, all course materials will be provided. Books get heavy when you carry them long distances, so it's best to leave them at home. However, be sure to bring along reading material for the trans-Atlantic flight. You will spend a full day getting to Europe, so having some portable entertainment will help occupy those long hours. It's much easier to carry some cash and an ATM card.
Banks charge a fee for cashing traveler's checks in Germany.
If you carry traveler's checks in American Dollars, you will also have to pay exchange fees. Personal checks are useless in Europe, so don't bring them. Traveler's checks, on the other hand, are safe and can be replaced if you lose them. If you prefer to take traveler's checks, use American Express and consider purchasing at least some of the checks in German Marks. No matter what, you will have to pay conversion fees.