From the website:
"The collection of Yiddish publications stem to a large degree from donations and consists primarily of fiction [...]
The Old Collection holds works printed 1600-1950, partly originating in the acquisition of David Simonsen's library (1932), partly from other donations, e.g. parts of the collection of the Bund Worker's Reading Room in Copenhagen (1967). Subjects: fiction, literary studies and editions, Rabbinic texts (translations/paraphrases).
The New Collection contains publications printed 1951 and later (catalogued 1971-).
Subjects: fiction, literary studies and editions
The Memorbikher (מעמורביכער, a.k.a. Yizkor-books, Zikhroynes, זכרונות) forms a special collection. Books primarily published after WWII and contaning documentation of the regions, cities and villages, where the Jewish population was wholly or partially wiped out in the Holocaust. Despite being part of the Yiddish collection, they often contain text also in other languages, e.g. Hebrew, but also languages relevant to the areas they document."
Consult the library catalogue here.