Demelza & the Spectre Detectors by Holly Rivers
Demelza loves science - she loves it so much that she's been known to stay up late to work on her peculiar inventions. But Demelza discovers she has inherited a distinctly un-scientific skill: Spectre Detecting. Like her grandmother, she can summon the ghosts of the dead.
But when Grandma is kidnapped by a mysterious villain, she knows Spectre Detecting has something to do with it. Only Demelza and her pasty best friend, Percy, can solve the deadly mystery.
Contemporary with a fantasy twist, this is thoroughly modern, charming and full of action - themes of death and the afterlife are handled with a light touch.