When visiting the library, make sure you park in a designated visitors' area. Parking tickets are not cheap at Bucknell, and you may find yourself with a $50 fine if you park in a staff or student area.
The closest visitor parking to the library is near the football stadium. You may park along Stadium Drive. To get to the library from there, walk through the Weis Building parking lot, heading Southeast. Walk between Coleman and Swartz Halls, then turn left. Walk up a slight grade, and the library will be on your right.
There are also two visitor parking spaces adjacent to Academic West (the building next to the library). These spaces fill up quickly, so the Stadium parking area is likely your best bet.