23 books • 2 series
Book #1: Riddles and Brain Teasers for Intelligent Kids
Book #2: Wacky Riddles and Brain Teasers For Clever Kids
Book #3: Challenging Riddles For Smart Kids
Book #4: Riddling Riddles For Incredibly Intelligent Kids
Book #4: 999 Fun and Challenging Riddles For Smart Kids (3 in 1)
Book #1: Trivia for Smart Kids!
Book #2: Trivia for Smart Kids (Part 2)