When Norman Ohler was just a kid, he and his grandfather were playing the board game Mensch ärgere Dich nicht, similar to Parcheesi. He and his classmates had just had one of their early-and-often lessons on the Third Reich, which perhaps even then included horrible footage filmed by American troops while liberating Buchenwald. Ohler wanted to know what his grandfather’s role was in Nazi Germany. So he asked. His grandfather disappeared for a few moments into the yellow house he’d built after the war on the edge of the small town Ohler grew up in. He returned to hand Ohler an envelope containing his Nazi party membership booklet and a swastika pin. He didn’t say much, and Ohler says he was too young to know what to make of this odd “inheritance.”

But he was aware that sometimes, when there was a problem in the democratic West Germany of the 1980s, his maternal grandfather would say that “under Hitler, this never would have happened,” or that “under Hitler, everything was in order.” Ohler’s grandfather portrayed the Nazis as “clean-cut.” Ohler would later discover that many Nazis, including Adolf Hitler, weren’t as clean-cut as his grandfather remembered.

His most recent book was released in the U.S. on Tuesday with the title and translation by Shaun Whiteside. It was (The total intoxication) in September 2015—and a Guardian Bookshop best-seller in the U.K. Publication rights for the work have been sold to 26 countries outside Germany, including Brazil, China, Israel, Japan and several in Europe. Ohler’s first nonfiction book argues—in more than two dozen different languages—that under the Nazi regime, German civilians were high, their soldiers were high, and their führer was high.