Norman Ohler joins us to discuss his book, Blitzed: Drugs in the Third Reich, which uncovers the history of drug use by Hitler and the Nazis during World War II and examines how this might have affected military operations. Ohler looks at how companies such as Merck and Bayer made cocaine, opiates and methamphetamine for military and civilian consumption. He also reveals that troops regularly took a form of crystal meth and that Hitler grew increasingly reliant on cocaine and heroin over the course of the war.   Norman Ohler will be in conversation with Rolling Stone editor Jason Diamond at the Community Bookstore (143 7th Ave., Brooklyn) on March 21 at 7 p.m. He will also appear at the Roosevelt House (47-49 East 65th St.) on March 23 at 6 p.m.