The red-lens decoder in the Game Book kept my 9-year-old busy for two hours straight, which never happens. She liked that she had to actually hunt for the hidden messages instead of just reading them. Bought a second set for her cousin's birthday.
Steven V.★★★★★
My 7-year-old spent an entire rainy afternoon with the decoder wheel book, refusing to put it down until she cracked every code. The red-lens pages in the other two are a nice change of pace, so there's enough variety to keep her busy for a while.
Harper A.★★★★★
The decoder wheel kept my eight-year-old busy for a full hour on our road trip, and she loved that the magic ink pages actually revealed hidden answers. The three different books give enough variety that she hasn't gotten bored after a week of daily use.