  The Ruppeiner metric as determined by the Hessian of the Gibbs surface
provides a geometric description of thermodynamic systems in equilibrium. An
interesting example is a black hole in equilibrium with its own Hawking
radiation. In this article, we present results from the Ruppeiner study of
various black hole families from different gravity theories e.g. 2D dilaton
gravity, BTZ, general relativity and higher-dimensional Einstein-Maxwell
gravity.
