The Hamburger Öffentliche Bücherhallen (Public Book Halls of Hamburg) are the system of public libraries in the city of Hamburg, Germany. They are the largest of such networks in Germany, serving a city of 1.7 million people with more than 100 branches of different sizes. Nevertheless, the stamp used by the library is quite modest.
It uses a simple, but striking red. Red is also used by the state and the city of Hamburg as official color. Besides that, the stamp is simple: The name of the library system, a known symbol for public libraries (an open book) in Germany and the gate used by the state and the city of Hamburg as their symbol, combined in a circle. You may would expect a more glamourous stamp from a system that large; but as the city of Hamburg prouds itself as being the centre of northern Germany and nothern Germany itself prouds itself with being direct, clear and uncomplicated, this stamp is quite fitting.