Triangular Sudoku : 150 Tridoku Puzzles, Paperback by Ape, D. J., ISBN 143825606X, ISBN-13 9781438256061, Like New Used, Free P&P in the UK

A collection of very refreshing new variant of Sudoku puzzles in triangular format is here, called TriDoku. Unlike in ordinary Sudoku, TriDoku puzzles are played on a triangular instead of a rectangular grid. But that's not the only difference! Instead of rows and columns, you have to use triangles and hexagons and so on... Instead of repeatedly solving classic Sudoku puzzles, this book offers you something to refresh your problem solving skills. There are 150 puzzles in this book, out of which 10 are TriDoku X (diagonal) and 10 Killer TriDoku puzzles, just to make things even more interesting!