If you’re looking for something more stimulating than a standard 9×9 Sudoku, you’re in the right place. The concept is the same, but instead of 1 through 9, you’re placing 1 through 25, using each number exactly once in each row, each column, and each bold-lined cube on the larger overall grid. Each puzzle has a unique solution and offers a new challenge.

Spiffy Activity Books Gigantic 25x25 Sudoku Example of puzzle on the left and filled solution on the right. "One puzzle per page with a clean, easy-to-read layout using clear, easy-to-read grids to prevent eye strain."
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Gigantic 25x25 Sudoku Volume 1 - Spiffy Activity Books - 120 puzzles designed for seasoned Sudoku solvers who find the traditional 9x9 puzzles too easy. [front book cover]Buy Now

Gigantic 25×25 Sudoku – Volume 1

★ Each puzzle has a unique solution and offers a new challenge.
★ One puzzle per page with a clean, easy-to-read layout using clear, easy-to-read grids to prevent eye strain.
★ Puzzles 1 through 20 gradually increase in difficulty, while puzzles 21 through 120 are more challenging.
★ Designed for seasoned Sudoku solvers who find traditional 9×9 puzzles too easy.
★ Requires a higher level of deduction and strategy than traditional Sudoku.

Gigantic 25x25 Sudoku Volume 2 - Spiffy Activity Books - 100 puzzles designed for seasoned Sudoku solvers who find the traditional 9x9 puzzles too easy. [front book cover]Buy Now

Gigantic 25×25 Sudoku – Volume 2

★ Each puzzle has a unique solution and offers a new challenge.
★ One puzzle per page with a clean, easy-to-read layout using clear, easy-to-read grids to prevent eye strain.
★ Designed for seasoned Sudoku solvers who find traditional 9×9 puzzles too easy.
★ Requires a higher level of deduction and strategy than traditional Sudoku.

The next volume in this series is scheduled for publication in mid-2026...