Text: The course is in good part based on the book ``The Universe in Gamma Rays'' by Volker Schönfelder (Springer Verlag 2002; ISBN 3-540-67874-3), augmented with material from G. B. Rybicki & A. P. Lightman: ``Radiative Processes in Astrophysics'' (John Wiley & Sons, 1979) and and M. S. Longair: ``High Energy Astrophysics'' (Vol. 2; Cambridge University Press 1997), as well as various web sites. The class will be largely based on powerpoint presentations, which will be posted on this web site. Therefore, none of the books is mandatory for this class, but I recommend them for further in-depth studies.