4 books · Ages 7–10 · Early Readers, Chapter Books
The Fourth Floor Twins is a 4-book series for ages 7–10 by David A. Adler. Each book stands alone — start anywhere.
Start anywhere — each book stands alone.
That said, The Fourth Floor Twins and the Disappearing Parrot Trick and The Fourth Floor Twins and the Fish Snitch Mystery are great first picks.
No particular order needed — browse and pick what catches your eye.