This summer, Sotheby’s is presenting Freddie Mercury: A World of His Own, a once-in-a-lifetime series of auctions in which Queen singer’s prized possessions go up for sale. Alongside his legendary public persona, Freddie Mercury was a deeply educated collector with a connoisseur’s eye, honed over years of careful research and exploration of the artists and movements that sparked his intellectual and aesthetic curiosity. This collection, given on his death in 1991 to his friend Mary...