Travel writer Robert Macfarlane, who chaired the judging panel, called "The Luminaries" ''dazzling," ''luminous" and "vast without being sprawling."
"It is beautifully intricate without being fussy," Macfarlane said. "It is experimental ... but does not by any means neglect the traditional virtues of storytelling."
Catton had been bookmakers' joint favorite among the six prize finalists, alongside British novelist Jim Crace, for his rural parable "The Harvest." She also beat Ireland's Colm Toibin, Indian-American writer Jhumpa Lahiri, Zimbabwe's NoViolet Bulawayo and Canada's Ruth Ozeki.
Catton received her trophy, which comes with a 50,000 pound ($80,000) check, from Prince Charles' wife, Camilla, the Duchess of Cornwall, during a dinner ceremony at London's medieval Guildhall.
"The Luminaries" centers on a man named Walter Moody who comes to a New Zealand prospecting town in 1866 and finds himself immersed in a web of saloons, seances and skullduggery.
The book's elaborate narrative is structured according to astrological charts: It consists of 12 sections, each half the length of the last, from a 360-page opener to a final chapter of a single page.
Macfarlane said the novel "takes place in a culture which is utterly capitalized" and focused on money, but also dwells on tenderness and love.
He said the panel of five judges met for two hours brief by Booker standards to choose the winner, which was decided without a vote. "No blood was spilled in the judging," he said.
Catton, who was 25 when she started writing the book and 27 when she finished it, has published just one previous novel. Now she has won a prize that brings a huge boost in profile, publicity and sales, and whose laureates include V.S. Naipaul, Margaret Atwood, Julian Barnes and Hilary Mantel.
The only previous New Zealand winner is Keri Hulme, who took the Booker in 1985 for "The Bone People."
New Zealand Prime Minister John Key said Catton's victory was "a hugely significant achievement on the world stage for a New Zealander."
Macfarlane said Catton's youth did not influence the judges, and Catton said she felt "honored and proud to be living in a world where the facts of somebody's biography doesn't get in the way of how people read their work."
This is the last year that the Booker founded in 1969 and officially named the Man Booker Prize after its sponsor, financial services firm Man Group PLC will be open only to writers from Britain, Ireland and the Commonwealth of former British colonies.
Beginning next year, Americans and other English-language writers will be able to enter as well.
The rule change aims to expand the global scope of the Booker even further, although some fear it may alter the delicate chemistry of the prize.
Macfarlane said "The Luminaries" was a fitting winner "a global novel that is always intensely local."
And its sheer size eight times the length of Toibin's 104-page "The Testament of Mary" had an added benefit for the judges.
"Those of us who didn't read it on e-readers enjoyed a full upper-body workout," Macfarlane said.
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Online: http://www.themanbookerprize.com/
Jill Lawless can be reached at http://Twitter.com/JillLawless
