German Language and Literature
Your best place to start is JHU's German Language + Literature Databases. Particularly useful for general literary research in German are:
Find scholarly articles easily. It's not everything out there, but it's a lot.
Set your Scholar Preferences for JHU, to be connected to online articles.
These are good collections to cross search.
Books on D-level
The main German Language and Literature collections are found on D-level at MSEL under the following call numbers:
PM (Compact shelving): Books on German language and literature, cataloged before 7/96.
PF 1-5999 (Blue Label Section): Books on German language cataloged after 7/96.
PT 1-4897 (Blue Label Section): Books on German literature cataloged after 7/96.