The top poetry award went to Us, then by New Zealand Poet Laureate Vincent O'Sullivan, while the illustrated non-fiction award went to Coast: A New Zealand journey by writer Bruce Ansley and photographer Jane Ussher.
The judges said Trevelyan's book - which followed her vivid biography of New Zealand artist Rita Angus -was "symphonic" and "a stunning book, brilliant in every respect".
Broadcaster Miriama Kamo, who convened a panel of five judges, said the book not only told the story of McLeavey's life, gallery, love of art, and deep friendships with artists - it also explored the emerging art scene in Wellington and across the country.
"Every part of it, from its writing and formidable research, to its illustrations and production through to its spirit, is in perfect harmony," she said.
"Jill Trevelyan's work is a bridge to a man who had a profound impact on the New Zealand art scene. This is not just a compelling read, it is a supreme achievement that delivers on every front."
The judges also lavished praise on Catton's second novel, calling The Luminaries sprawling and brilliant.
"There's a virtuosity to the work that affirms every accolade, that justifies all praise. Eleanor Catton is an extraordinary writer who has conducted a bold experiment and, in the tradition of great and celebrated risk-takers, it has paid off richly."
The judges said O'Sullivan's poetry was "honed and sensuous" and simply got better and better. They also praised illustrated non-fiction winner Coast as "spectacular" and an epic work that should be in every New Zealand home.
Trevelyan's book beat three other non-fiction finalists -- Lloyd Jones' A History of Silence, Rebecca Macfie's Tragedy at Pike River Mine, and David Grant's The Mighty Totara: The life and times of Norman Kirk.
Catton's novel won over three fiction finalists -- Anne Kennedy's The Last Days of the National Costume, Charlotte Randall's The Bright Side of my Condition, and Damien Wilkins' book Max Gate.
The judging panel - which included broadcaster Kim Hill, artist Dick Frizzell, writer Elizabeth Smither, and literary critic Peter Simpson - said they were impressed by the standard and variety of titles.
Kamo said the competition was tough, but the winning books were without doubt the best of the year.
NZ POST BOOK AWARD WINNERS
Book of the Year ($15,000 prize)
Peter McLeavey: The life and times of a New Zealand art dealer by Jill Trevelyan (Te Papa Press)
General non-fiction ($10,000 prize)
Peter McLeavey: The life and times of a New Zealand art dealer by Jill Trevelyan (Te Papa Press)
Fiction ($10,000 prize)
The Luminaries by Eleanor Catton (Victoria University Press)
Poetry ($10,000 prize)
Us, then by Vincent O'Sullivan (Victoria University Press)
Illustrated non-fiction ($10,000 prize)
Coast: A New Zealand journey by Bruce Ansley and Jane Ussher (Random House NZ/Godwit)
Nielsen Booksellers' Choice ($2500 prize)
Molesworth: Stories from New Zealand's largest high country station by Harry Broad and Rob Suisted (Craig Potton Publishing)
People's Choice ($5000 prize)
The Luminaries by Eleanor Catton (Victoria University Press)
New Zealand Society of Authors best first book ($2500 prize each, announced 16 July)
Tough by Amy Head (Victoria University Press)
Horse with Hat by Marty Smith (Victoria University Press)
Tragedy at Pike River Mine by Rebecca Macfie (Awa Press)
