Frequently Asked Questions

Every puzzle in the book is a high-quality, honest Sudoku puzzle solvable with logic alone. However, 20 of those puzzles contain a single shaded cell. The digits inside those shaded cells spell out passwords that unlock 3 secret vaults on this website!

Yes! Full answer keys for all 200 puzzles are included in the back of the book, alongside an enciphered spoiler protection key.

You can visit our Hint Chamber for progressive, spoiler-free clues that help you find the key digits and decode the words without ruining the surprise.

No! Email is strictly optional. When you crack a vault, your reward PDF (50 Easy, 100 Medium, or 200 Hard puzzles) is available for direct instant download. We never gate your rewards behind email collection.

There is — and the Keeper would rather you found it yourself. It is never announced in the book, and no one who reads only the puzzles will stumble into it. The way in is written across the Keeper's three letters, for anyone who reads them the way a codebreaker would.

Truly stuck? The Hint Chamber will take you the rest of the way — but the discovery is sweeter unaided.

Yes. PuzzleSecret contains zero tracking scripts, zero third-party ads, zero dark patterns, and zero external font tracking. All font assets are self-hosted directly on our servers. The puzzles themselves suit any age, but our newsletter and the Keeper's Register are for solvers aged 13 and over, and we never ask any visitor for their age, school or location.

The artwork was, and the puzzles were not. The vault illustrations on this site and the engraved border art in the book were created with Google Gemini and then hand-edited. Everything that makes the book work — all 200 Sudoku puzzles, the ciphers, the Keeper's letters and the hunt itself — was built and verified by a human. Every puzzle is machine-checked to have exactly one solution.

Volume 1 is available in paperback on Amazon Prime worldwide.