Sammy Keyes and the Skeleton Man
by W. Van Draanen (1998)
Sometimes an author puts in too much, this one is a mystery and a revenge story all rolled together, and the two parts really have nothing to do with each other.
Sammy is misfit teenager being bullied by the cool girls while illicitly living with her grandmother in the ol' folks home and solving a family feud/attempted murder/theft of rare books... The crime solving stuff could have been much better and made a more complete book if most of the teen girl drama material would have been saved for another book.
That said, Sammy and cohorts are attractive and entertaining characters, I'd probably get more into the book if I'd read her backstory and followed the series from the beginning rather than somewhere in the middle.
Comments from the author, including the word "prevarication" !