This four-part tutorial at NeoLib guides you through planning for and measuring the effectiveness of a library website:

A Brief Intro to Web Analytics and Web Optimization for Libraries Pt 1
A Brief Intro to Web Analytics and Web Optimization for Libraries Pt 2
A Brief Intro to Web Analytics and Web Optimization for Libraries Pt 3: Social Media
A Brief Intro to Web AnaAlytics and Web Optimization for Libraries Pt 4: What Do They Think of Us?

It’s a good reminder that formal evaluation is important throughout your design process, no matter what you are designing.