"I never understood what makes me so special, " mused Audrey Hepburn. The daughter of a Dutch baroness, Hepburn first won international acclaim with her role as a princess in the 1953 film Roman Holiday, and she maintained a rare grace and elegance throughout her life that millions have adored and tried to emulate. Audrey Hepburn: A Photographic Celebration showcases the film star, who also wor…