“The Making of ‘Queen of the Air’”  Set in the early decades of the twentieth century, “Queen of the Air” tells the story of aerialist Lillian Leitzel and trapeze artist Alfredo Codona, lovers and the most famous stars ever to perform beneath the big top. As in Greek tragedies, partly because of the intervention of gods, but also because of the protagonists' human frailties, Leitzel and Codona would both come to violent ends, and the circus, maybe nearly an eternal institution, would never again be the same. For the last 25 years, Dean Jensen has been operator of a contemporary art gallery in Milwaukee, the eponymously named Dean Jensen Gallery, and before that, an art critic and feature writer for the Milwaukee Journal Sentinel. He is the author of four books, the latest of them “Queen of the Air: A True Story of Love and Tragedy at the Circus.”