  We present a detailed discussion of AdS_3 black holes and their connection to
two-dimensional conformal field theories via the AdS/CFT correspondence. Our
emphasis is on deriving refined versions of black hole partition functions,
that include the effect of higher derivative terms in the spacetime action as
well as non-perturbative effects. We include background material on gravity in
AdS_3, in the context of holographic renormalization.
