3 books · Ages 7–14 · Chapter Books
Usborne Solve It Yourself is a 3-book series for ages 7–14 by Phil Roxbee Cox. Each book stands alone — start anywhere.
Start anywhere — each book stands alone.
That said, The Haunting of Dungeon Creek and Whatever Happened to Professor Potts? are great first picks.
No particular order needed — browse and pick what catches your eye.