There are a few libraries in Boise, here are a couple:

Academic

The Boise State Albertsons Library focuses on academic needs of the students and faculty of Boise State University. It has over 300 databases with academic articles, paper books and an increasing number of eBooks. 

Public

The Boise public library system has several branches. The downtown branch may be considered the "main" branch. They have a pretty solid film and TV DVD collection, graphic novels, books, though you may need to put popular items on hold. The website (now) tells you how many other people are in the hold line in front of you.

Technically the Albertsons library is public too - although it's geared towards students, community members can check out some materials and get a library card.