This is a rather large book with different puzzles, riddles, and mind challenges. I would say this book could be appropriate for 3rd-5th graders. Some of these puzzles had me stumped, and this could be a good whole group activity where students try to come up with answers. This is really engaging and get people thinking. You could even do a "Riddle a Day" or something, where everyday you read aloud a riddle and give students time thing ponder about them. I also really love how they have the answers on the back.