Bibliotheek is the Dutch word for library. Unlike in the US, most libraries don’t have a large genealogical collection. Most will just have one or two general genealogical reference books in their collection plus some local history books. Only major libraries will have a subscription to genealogical journals such as Gens Nostra or De Nederlandsche Leeuw [the Dutch Lion].
To find genealogical collections, visit an archive (archief) instead.