The university library at Harvard University contains 16.6 million books in its shelves. Harvard’s library is the world’s best equipped library and was founded in 1638 by John Harvard. 400 books of John Harvard’s ownership were the cadre for the library. In the next century the amount of books grew to one of the largest libraries in America. Unfortunately a fire in 1764 destroyed almost the whole inventory. Thanks to donations the library could be rebuilt. Today 79 libraries belong to the HUL (Harvard University Library).
For comparison: the library of the Humboldt-University in Berlin is the largest university in Germany, with three to four million books available.