Why did self-made billionaire David Siegel decide to build the nation's largest single-family dwelling? "Because I could," he explains with serene self-assurance. The 90,000-square-foot mansion near Orlando's fantasy kingdom Disney World is designed to include a grand ballroom for 500 guests, a 20-car garage, 10 kitchens (one exclusively for sushi), and a roller-skating rink.

That if-you-got-it-flaunt-it comment, at the opening of Lauren Greenfield's superb documentary "The Queen of Versailles," sums up the buoyant, delusional exuberance of pre-crash America. The film follows Siegel and his wife, Jacqueline, a former beauty queen 31 years his junior, through the financial crisis as construction halts on their faux-French palace (dubbed Versailles but modeled on the Paris Hotel in Las Vegas). It's an astonishingly candid, surreal, unsparing yet sympathetic fly-on-the-wall view of life among the One Percent. It's "Real Housewives" meets "Citizen Kane."

Jackie, who confesses to a $1 million-a-year personal shopping habit, grew up middle-class and doesn't put on airs. Greenfield lays out Jackie's background as an ambitious student who excelled at computer science and landed an engineering job at IBM. The striking blonde soon realized she could rise further through her looks than her professional attainments. She became a swimsuit model and wife of a wealthy Floridian, split from him and climbed the next economic rung through her marriage to Siegel, whose Westgate resorts time-share empire made him one of the nation's wealthiest men.

Atrocious oil portraits depicting the 70-something mogul and his busty, Botoxed wife as French royalty and Roman warrior and damsel redefine the term kitsch.

Westgate expanded into an empire in the era of easy credit, and the Siegel family grew to eight children, including an adopted niece. With the kids whizzing around their 26,000-square-foot starter mansion on Segways, it clearly was time to upsize.

The 2008 financial crisis shattered the tower of debt sustaining the company. David had put every penny into his business, and when it tanked, Jackie's insatiable spending downshifted from Versace to Wal-Mart. Construction on Versailles halts, leaving an uninhabitable shell. They lay off most of their servants and Jackie, who David describes as "another child," does her ditzy, endearing best to manage her kids, innumerable pets and household details.

It's a daunting challenge for a woman accustomed to a life of unchecked privilege. Jackie frets that the kids might now have to go to college. She travels to her childhood home on a commercial flight where the children ask who are all those strangers on their plane, and dumbfounds the airport Hertz car rental agent by asking if a chauffeur is included. In Florida the family steps around pyramids of dog poo -- it used to be someone's job to pick that up -- and encounters dead, forgotten pets the pampered kids neglected to feed.

The film draws a poignant portrait of the relationship between the Siegels and their dwindling, loyal household staff. Jackie didn't think she'd have more than one child, but once she found out she could hire nannies, she didn't see any reason to stop having children. The helpers have great affection for the couple and their kids, but their gratitude seems disproportionate to their compensation. Nanny Virginia Nebab, who lives in a giant back-yard playhouse that the Siegel children no longer use, movingly describes how hard it is to provide for her own family back in the Philippines. Neither she nor her employer does well by their own children, one because of too little money, the other because of excess.

"The Queen of Versailles" is beautifully constructed and frequently uproarious. It's not derisive laughter directed at the Siegels' comeuppance. David speaks emotionally about disappointing the thousands of Westgate employees he was forced to lay off. Jackie is as openhearted, down-to-earth and charitable as she is clueless. The film's abundant humor comes from the insane excess of their overreaching pre-crash lifestyle and the incongruity of a humbled mogul grousing at his children to turn the lights off when they leave a room.

Colin Covert • 612-673-7186