Binney has cleary established Galactic Dynamics and its companion volume Galactic Astronomy as the definitive works on the subject. The NASA Astronomy Abstract Service lists 3411 citations for this book as of 12/2006 so it is clearly an important part of the literature of astrophysics.
This book is written at the graduate or researcher level. As it deals with the behavior of galaxies, potential theory, energy distribution, angular momentium and dark matter so the mathematics employed are quite powerful.