Good beer...that's about it.
Be prepared to wait up to half an hour for a drink after your first couple, especially as the evening goes on and the bar gets busier. I've taken to ordering two at a time when I find myself at the Library. Also be prepared to wait at LEAST fifteen (usually more like thirty) minutes to get your check and be able to pay out.
The afternoon servers are mostly very friendly and fast, but the evening servers are mostly snotty and will deliberately ignore female customers. Guys get WAY better service, even when it comes to female customers who are regulars and big tippers. It's actually quite offensive. I avoid the Library as much as possible these days, as the service has gotten so progressively worse over the last few years.