On the cusp of the United Nations’ 60th anniversary, the organization’s stewards began to plan a long-overdue renovation of its three main buildings. The 18-acre campus on Manhattan’s East Side was plagued by asbestos, outdated HVAC systems, deteriorating glass facades, and decades of cigarette smoke coating the walls. There was talk of tearing down and starting over, but in the end, the iconic International Style buildings were deemed preservation-worthy. The massive undertaking took 6 years, a process documented in The United Nations at 70: Restoration and Renewal (Rizzoli, $55), a celebratory monograph released earlier this month that features an architectural history written by Carter Wiseman.