Are other people having the same problem? If so, find out. There is strength in numbers. I would consider writing to your local newspaper as well. The way I see it, libraries are funded in part, if not mostly, by tax payers and people who contribute with the idea that they are helping a good cause. So the community owns the library, the people at the library are working for you. In some towns, the library boards are run by elected officials so they have a duty and repsonsibility to hear compliments and complaints.
I would write the letter, as I would think I would be doing a service to my community by trying to improve a system that is failing.