Most of the volumes are in superlative condition; some have never been read, and their pages remain uncut. Unusually, most have their original, highly decorative bindings; many copies from this period were rebound during the 18th and 19th centuries, when owners had different tastes in book bindings.
Sotheby's princely collection comes from a princely source - one of the most important court libraries, in the Baroque castle, Donaueschingen, Baden-Wurttemberg. It is a library founded by Wolfgang, Count Furstenberg (1465-1509) and sold by his descendant, Joachim Prince zu Furstenberg, a member of one of Germany's largest land-owning families.
Among unique items in the collection, which will be sold in July, is a 1462 Viennese calendar for blood-letting, indicating the best days in each month for bleeding different parts of the body.
It was designed for popular use and, when a new calendar became available each year, the previous one would be thrown away. This one survived only because it was used as binding.
Charlotte Brown, a deputy director of Sotheby's, said that until this piece was studied, 'printing was only known in Mainz and Bamberg. This is evidence that printing was going on in Vienna, too'.
Another unique piece is a 1473 German language Ars Moriendi, the art of dying - a 'blockbook' in which each page was carved from a block of wood, rather than using movable type.