From the Wikipedia page on the the University of Bonn 
The university library was founded in 1818 and started with 6,000 volumes inherited from the library of the closed University of Duisburg. In 1824 the library became legal deposit for all books published in the Prussian Rhine province. The library contained about 200,000 volumes at the end of the 19th century, and about 600,000 volumes at the outbreak of World War II. An air raid on October 10 in 1944 destroyed about 200,000 volumes and a large part of the library catalog. After the war the library was housed in several makeshift locations until the completion of the new central library in 1960. The new building was designed by Pierre Vago and Fritz Bornemann and is located close to the main building. In 1983 a new library building was opened in Poppelsdorf, west of the main building. The new library building houses the science, agriculture and medicine collections. Today the university library system the central library, the library for science, agriculture and medicine and about 160 smaller libraries. The university library holds 2.2 million volumes and subscribes to about 14,000 journals.