I second Captain Birdseye's reservations.

I attended a folk club (to hear some friends play) where the booked artist was a young man who sang his own songs of teenage angst for 40 minutes that seemed like a lifetime of torment - however he had brought his own fan club base who obviously enjoyed his performance.

This person was, I hasten to add, a skilled muscian and I enjoyed his treatment of the one or two songs he performed that were not his own.

It is important to find out what kind of material someone performs both for the people booking artists AND the potential audience themselves.