Debut author Anna Funder has won the BBC Four Samuel Johnson Prize for her book about the hardships endured by people from the former East Germany.
Ms Funder's book has sold 5,163 copies so far
The book, titled Stasiland: Stories From Behind the Berlin Wall, earned Funder £30,000 in prize money.
The chair of the judges, TV writer Michael Wood, said Stasiland was "a beautifully executed first book".
Other finalists for the prestigious non-fiction prize included travel writer Bill Bryson and Anne Applebaum.
The judges announced the winner at an awards dinner at the Savoy Hotel in London on Tuesday.
"Anna Funder's Stasiland is a fresh and highly original close-up of what happens to people in the corrosive atmosphere of a totalitarian state," said Mr Wood.
He described it as "an intimate portrait - both touching and funny - of survivors caught between their desire to forget and the need to remember".
Martin Higgs, literary editor for book retailers Waterstone's, said: "Funder has a strong journalistic style and writes about real lives in a real way."
SAMUEL JOHNSON PRIZE SHORTLIST 2004
Anna Funder (winner) - Stasiland: Stories From Behind the Berlin Wall
Anne Applebaum - Gulag: A History of the Soviet Camps
Jonathan Bate - John Clare: A Biography
Bill Bryson - A Short History of Nearly Everything
Aidan Hartley - The Zanzibar Chest: A Memoir of Love and War
Tom Holland - Rubicon: The Triumph and Tragedy of the Roman Republic
Source: Colman Getty
Anna Funder was born in Australia in 1966 and grew up in Melbourne and Paris.
She was a lawyer and radio and television producer before becoming writer-in-residence at the Australia Centre in Potsdam, Germany, in 1997.
Stasiland was also shortlisted for the Guardian First Book Award.
Past winners of the Samuel Johnson Prize, now in its sixth year, have included Michael Burleigh for his book about the Third Reich and TJ Binyon for his biography of Russian poet Alexander Pushkin.
This year saw 120 books submitted, which were whittled down to a longlist of 23 before the shortlist of six was chosen.
Bill Bryson won the prestigious 2004 Aventis Prize for popular science books earlier this week.
His book, A Short History of Nearly Everything, is an exploration of science for people who found school lessons "boring and mystifying".
Mr Bryson was presented with a cheque for £10,000 during a gala dinner at the Royal Society in London on Monday.