4 books · Ages 3–9
Knowing the Difference is a 4-book series for ages 3–9 by Baby Professor. Each book stands alone — start anywhere.
Start anywhere — each book stands alone.
That said, The Difference Between Horses, Donkeys and Mules and The Difference Between Meteors and Meteorites are great first picks.
No particular order needed — browse and pick what catches your eye.