Pros
Depending on the branch you work in, coworkers can be utterly amazing, a lifeline in such a low-paid profession. Benefits such as vacation and sick leave are generally much better than most companies give. And all in all, the job is incredibly rewarding in a lot of ways (except financially) and quite a lot of fun. I sometimes find it unbelievable that we get to move books around all day while helping maintain society's greatest achievement--the public library.
Cons
Low pay and lack of respect. It's hard work that requires a lot of expertise, but no one's willing to recognize you for it in a way that would actually make a difference. While the lowest-paid employees rush around--processing thousands of items, helping patrons, and generally keeping the library running--those who actually make a living wage either sit in their offices or talk with each other throughout their shift. If you're in circulation, you're often treated by the higher-ups as if you don't know anything, even though you're often fielding questions not just from patrons, but also from the information specialists. There needs to be more opportunity for advancement in this organization and better treatment of branch staff, or else it will continue hemorrhaging circulation staff who burn themselves out doing such rigorous work every day and waiting for recognition that never comes.