Three Sudoku puzzle books are on the New Zealand adult international non-fiction best seller list, which has been described as "unusual".
Booksellers New Zealand promotions co-ordinator Holly Robinson said the puzzle books were "certainly very popular".
"People are devouring these things.
"It doesn't matter what else New Zealanders are doing,
they're certainly doing Sudoku," she said.
"It goes to show once a day in the paper just isn't enough."
Ms Robinson said puzzle books don't usually feature on best-seller lists but Sudoku seems to be the exception.
Sudoku puzzle books have been a regular feature on New Zealand best seller lists since August.
The puzzles first began appearing in newspapers around the world in late 2004.
The object of Sudoku is to fill in a 9x9-square grid so that each column, row and nine smaller 3x3 grids contain the digits 1 through 9.
It requires no mathematical skill, and eliminates the language barriers of other puzzles.
First published in an American magazine in the 1970s, Sudoku was based on Latin Squares, a puzzle devised by Leonhard Euler, a Swiss mathematician, in 1783.
It became popular in Asia and a New Zealander, Wayne Gould, a judge who had moved to Hong Kong, spotted a book of the puzzles while shopping in Tokyo in 1997.
He enjoyed the puzzles so much he developed a software program to generate them and convinced the Times newspaper to publish them. The rest, as they say, is history.
Sudoku is popular with people of all ages.
It does not require prior knowledge, is all simply logic and can be easily solved by a process of elimination.
- NZPA
Top 10 Best-selling international non-fiction
1: A Short History of Nearly Everything, Bill Bryson (Doubleday) 2: Sudoku 1 (Highly Addictive) (Hinkler Books)
3: It's Not About the Bike, Lance Armstrong (Allen & Unwin)
4: Allen Carr's Easy Way to Stop Smoking, Allen Carr (Penguin Books)
5: Sudoku 3 (Highly Addictive) (Hinkler Books)
6: The F2 Diet, Audrey Eyton (Bantam Press)
7: Sudoku 2 (Highly Addictive) (Hinkler Books)
8: The Great War for Civilisation: The Conquest of the Middle East, Robert Fisk (Fourth Estate)
9: Who Moved My Cheese, Dr Spencer Johnson (Vermilion)
10: He's Just Not That Into You, Greg Behrendt & Liz Tuccillo (Element Books)
Source: Booksellers New Zealand
