Killer Sudoku Book Vol 1 & 2

New to killer sudoku? Here is an explanation of the rules of the game:

The book contains 100 puzzles. There are 34 easy killer sudoku, 33 medium and 33 hard puzzles in this book. So whatever your experience with killer sudoku, there is a puzzle for you!

The key to solving killer sudoku is to use the information provided by the sum regions (the dotted cages) to help you whittle down the possible values for the cells in the grid, and then combine this information with the familiar sudoku solving rules in order to complete the puzzles. There are some rules unique to killer sudoku that you'll need to know, particularly with the harder puzzles. The introduction to the book tells you the rules of the game, and the how to solve outlines the Rule of 45 - which is a piece of logic you'll need to help you solve some of the harder puzzles in the book.

All the solutions are included at the back of the book so there is help if you get stuck; and also rest assured that if you do find it hard to make progress you should persist - as each and every of the 100 killer sudoku puzzles in the book has just one solution, and it can be found through logic alone; you'll never need to guess to solve these puzzles, although some of them are tricky to crack!

If you would like to try a few of the puzzles before buying this book, please click the link below:

Killer Sudoku Sample

The book of Killer Sudoku is available to purchase right now from Amazon.co.uk, Amazon.com and Amazon.eu. Please click the relevant link below to purchase this book via Amazon:

Solving Killer Sudoku

The first is to learn the combinations of numbers that have the least options: there are tables available on the internet that contain the various different ways that certain numbers can sum together and these are very useful. For instance, if you have to make 17 from two squares in a killer sudoku, then you know straight away these contain the 9 and the 8 so they can be written in as pencilmarks and removed as options from all the other squares in the grid.

Other combinations might be less obvious but equally restrictive - such as making 15 off 5 squares, there is only one way to do this: it must be 1,2,3,4,5. There are also various quirks of sums with lots of options: perhaps only 7 of the 9 numbers can be used to make that particular sum from all the various other combinations that fit. An awareness of mathematical facts and sums such as this can help to solve killer sudoku quickly rather than struggling away trying to work out all the combinations.

A rule used in killer sudoku but not normal sudoku and alluded to briefly in the main description above is something called the rule of 45. This reminds you that the numbers in each region sum to 45, since that is the sum of 1 to 9. This can often be used to help you place certain numbers straightaway, or at least reduce options. Let's take a look at this rule in operation.

Open the sample PDF via the link above called 'Killer Sudoku Sample' and look at the first row of puzzle 1. You can see the first three caged regions are all in row one, and sum to 5, 13 and 13 respectively: that's 31 in total. So now we know the final two squares in the row must sum to 45 - 31 = 14. Now, they are in cages that sum to 6 and 12 respectively. the maximum value for the 6 cage from two squares is clearly 5, since 5 + 1 = 6. But wait a minute - if the value were only lower than 5, say it was 4, then the final square would have to contain 10 to complete the sum to 45. Not possible! Therefore we can instantly write in 5 and 9 as the final two values of the row, just like that... how easy was that! By using the rule of 45 astutely you can crack killer sudokus much more quickly than just by using standard sudoku solving rules. Got any other tips? Let us know!

Here is a visual explanation of the killer sudoku rule of 45: