14 books • 2 series
Book #1: Difficult Riddles And Brain Teasers For smart kids ( And For The Whole Family)
Book #1: Difficult Riddles And Brain Teasers For kids
Book #2: Difficult Riddles And Brain Teasers For Smart Kids ( And The Whole Family)
Book #2: Brain Exercises For The Whole Family
Book #3: Difficult Riddles And Brain Teasers For Smart Kids ( And The Whole Family) Volume 2