A sequel to "A Bad Case of Ghosts". Giles Barns and his friends Kevin and Tina Quark (who are geniuses) come across some strange occurrences in their library. At first they think they are dealing with ghostly goings-on, but further investigation reveals that there is another kind of magic afoot.
This book is part of the Barnes and The Brains Books series and is book #3 in the series.