The anthology Myths, Masks, and Subjects provides a good and broad introduction to the theory and fields of application of critical whiteness studies in Germany.
Maureen Maisha Eggers, Grada Kilomba, Peggy Piesche, Susan Arndt (eds.) 2005: Myths, Masks and Subjects. Critical Whiteness Research in Germany. Münster: Unrast.
If you don’t have a bookstore worth supporting near you, you can also buy the book from the alternative non-profit online bookstore links-lesen.de, which supports political projects with the profits. The link to the book can be found here.