Princeton Public Library

Library hours are

Monday - Thursday 9:00 a.m. - 9:00 p.m.
Friday and Saturday 9:00 a.m. - 6:00 p.m.
Sunday 1:00 p.m. - 6:00 p.m.

(from official website)

You can return books and DVDs at the library; just in front of the post office on Palmer Square; and at a box next to the dinky station.

The library has free internet.