What is the theme in Eyewitness Auschwitz: Three Years in the Gas Chambers by Filip Muller?

The central theme and dominant feature of the text is the Nazi-perpetrated Holocaust, the genocide of Jews and other minority groups of Europe and North Africa. The most-commonly cited figure for the number of Jewish victims murdered is six millions, though estimates range from five to seven millions. Muller estimates that Auschwitz killed about 1.1 million people during his incarceration, over 400,000 of whom were Hungarian Jews. In addition, other minorities were also murdered—Muller mentions gypsies, Soviet soldiers, political prisoners, and discontented German citizens. The Holocaust is sometimes defined as limited to the genocide of the Jews but many consider it to include the mass genocide of all targeted groups. Thus the most inclusive definition places the total number of Holocaust victims at nine to eleven millions with some estimates as high as twenty-six millions. Muller presents this as eyewitness testimony.