“Puzzle Communication Nikoli Vol.189”
Nikoli is the most advanced pencil puzzle magazine in Japan. The first issue was published in August, 1980.

“ChoGekikara (Really really hard) Sudoku 16”
“Cho-Gekikara (Really, really hard) Sudoku” contains 91 sudoku puzzles.

“Nankan(Hard)Sudoku 16”
“Nankan (Hard) Sudoku” contains 105 sudoku puzzles.

“Have a Ball with Pencil Puzzles – Slitherlink4”
This book contains about 90 slitherlink puzzles ranging from easy to hard.

“Have a Ball with Pencil Puzzles – Kakuro 4”
This book contains about 90 Kakuro puzzles ranging from easy to hard.

“Medium Sudoku Best Selection”
This book contains 116 Sudoku puzzles, all of medium difficulty.
These puzzles were published in the NIKOLI “Sudoku Communication” and have been re-edited with the excellent results published here.

“Sudoku Strategy Guide (Revised Edition)”
This is a revised edition of the “Sudoku Strategy Guide” published by Nikoli in 2007. It will satisfy everyone from beginners to those who want to be able to solve more difficult problems.