Beat this: children must find up to 100 differences in each odd one out puzzle in record time! It's not easy to solve them--but it's such a thrill, kids will keep coming back for more. When completed, favorites can be colored too. Each of the books in the Challenging... Books series is jam-packed with puzzles that are entertaining and absorbing. Plus, there are time challenges with every puzzle, so kids can try to beat the rest of the best. The only question is... are they up to the test? Encourage them to say yes, and tell them to get ready for hours of stimulating fun!