To search the library catalog for different language materials, you can use the language filter on the Advanced Search page of the Book and eBooks Catalog.
From the library's home page, get to the Catalog by clicking Find Books and eBooks.
Use the Language filter by selecting German from the drop down menu. This filter option is usually right below the search bars, but sometimes will appear at the bottom right of the page.
At this point you can search, or use the keyword search to limit your results by any topic you are interested in.