The library is really two bars. Downstairs, it caters towards what I would call the typical "high-end" South Siders. There's a lot of TVs with sports, and a lot of dudes wearing too much cologne, and chicks with crunchy hair. The tenders a tad stingy, particularly with drink-and-mixer cocktails. Upstairs, however, is more boheme. The pool table area has its own small bar, as does a hidden patio. My favorite room is the large dining area upstairs. They typically have great, local art on display (and sale), and on Fridays and Saturdays, the waitstaff is quick and friendly.
A big draw for the Library is the food. Not only is it literary in its name, it's unlike typical bar fare. The sandwiches are stellar. I recommend the George Orwell/Animal Farm sandwich. And the Edgar Allen Potatoes are excellent as well.
All in all, I would rate the upstairs of the Library five stars if you're searching for a low-key, fascinating place to sit and talk. I would rate the downstairs three-stars, as it really is just another SS bar.