Of all the corpora of surviving Germanic writings, Old Norse literature is by far the largest and most complete.
The sagas represent the largest share of surviving Old Norse literature. They are epic and scope and written in prose, although they often have alliterative poems embedded in the text. They were for the most part written down in the 13th and 14th centuries; the topic of whether they simply represent the transcription of earlier oral works or distinct literary creations is still debated.
The sagas vary widely in subject matter, from the feuds of everyday farmers in Iceland around the turn of the millennium to more distant and legendary tales of heroes stretching as far back as the Migration era; they share in common a preference for the exploits of believably human characters, rather than gods or other supernatural beings. Although some of the sub-genres of saga are distinctly Norse, many sagas make use of common motifs and legends of Germanic culture, and even begin to show some overlap with distinctly later genres as hagiography and romance.
Even more widely varied than the sagas is Norse poetry. You can read all about it when I've finished this article.