Looking for a new challenge? STAR BATTLE is my latest addition. Check it out!

Insane Killer Sudoku, 4-per-page, Volume 9

Each booklet contains a collection of eight different puzzles, 1-per-page, with a page of answers in the back. The booklets are ordered by ascending difficulty -- the puzzles in book 100 are much harder than the puzzles in book 1. All these puzzles have a single unique solution.

These puzzles are in PDF format and need the Adobe Acrobat Reader to view or print.

You can also download all 800 of these puzzles, in the 4-per-page format ( with hints and answers, with answers but no hints, or with neither hints nor answers).

Want to save even more trees? Try the online version of these puzzles.

Here's a handy cheat-sheet of candidate cage sets that makes it easier to eliminate numbers.

Problems printing puzzles? Try these work-arounds.

Out of insane puzzles? Here's 800 more!.