The FBI recently discovered their independence thinking when it was told officially by the ALA to stop trying to enlist librarians to track the reading and borrowing habits of certain patrons. Academic libraries still prefer hardcover for most titles and special libraries often have no preference. For example, many corporate and technical collections just want the latest and best research material as soon as it's available, regardless of format. Individual libraries also buy multiple copies of current interest titles if circulation demand is high or if they want to place one in the reference collection and others in general circulation. Furthermore, library sales are not subject to the devasting returns problem that is so damaging in the trade and to a lesser extent in the college adoption market.
Libraries also order more titles at one time and they almost never fail to pay their bills.
Librarians don't want trade puffery because they're mainly interested in the facts - straight information on which they can make a rational buying decision. Multicopy purchases are common. The Baltimore County system recently ordered 1500 copies of a Danielle Steele novel before publication. Even small libraries buy several copies of high-circulation titles and then may but two or more of a reference work such as a tax guide. One can then be anchored in the reference department while the others are circulated to the public.