Berghahn, V. R., Imperial Germany, 1871-1914, Berghahn Books, 1994.

Berghahn provides a history of the German empire,
from its formation in 1871 until the beginning of
World War I.

Hesse, Hermann, Soul of the Age: Selected Letters of Hermann Hesse, 1891-1962, Farrar, Straus and Giroux, 1991.

Soul of the Age is an edited selection of the letters of
Hesse, including his correspondence with such notables
as the writers Thomas Mann and André Gide,
and modern Jewish philosopher Martin Buber.

Marrer-Tising, Carlee, The Reception of Hermann Hesse by the Youth in the United States: A Thematic Analysis, P. Lang, 1982.

Marrer-Tising offers discussion of the popularity of
Hesse's novels among American youth during the
1960s and 1970s. Marrer-Tising explores thematic elements
of Hesse's fiction which addressed ideas and
concerns of the youth counterculture during this era
of U.S. history.

Michels, Volker, ed., Hermann Hesse: A Pictorial Biography, Farrar, Straus...