The Big Book of Logic Puzzles - Suguru 400 Hard (Volume 1)

Suguru ("Number Blocks") is a logic puzzle invented by Naoki Inaba (Japan) that has simple rules, but which provides sufficient challenges to satisfy the most enthusiastic solvers!. The task consists of a rectangular or square grid divided into regions. Each region must be filled with each of the digits from 1 to the number of cells in the region. Cells with the same digits must not be orthogonally or diagonally adjacent. Even though the rules are simple, you will need all your skills to solve it.