Sometimes people will ask who orders our books, and the answer is a diverse mix of people. Each department is allocated money to buy books (and media etc.) with. Each department has a library coordinator who is one half of the link between the department and the library; the other half is the librarian who is the liaison to that department.
So, the various faculty order materials, the librarian liaisons order some titles, other people in the library process and catalog the materials, and then they appear on the shelves for you to use.
You may be interested to know that we have the largest book collection of all the SUNY four year schools!