Not only music lovers will find this recently published book by Monika Woitas most interesting:
Geschichte der Ballettmusik. Eine Einführung
It outlines the development of the genre from its beginnings in Italy through the prestigious ballets at the court of the Sun King, great ballet classics of the 19th century such as Giselle or Swan Lake up to the manifold forms of ballet music in the 20th and 21st century.