I just finished a great book - it's a children's book, but I think that adult mystery fans will also enjoy it. It's Down the Rabbit Hole: An Echo Falls Mystery by Peter Abrahams. It's the story of Ingrid Levin-Hill, a 13 year old soccer player, aspiring actress, and Sherlock Holmes fan. When a local eccentric woman is murdered, Ingrid finds herself in the situation of having to solve the murder without implicating herself. She must do this while struggling with algebra, playing soccer and starring as Alice in the local production of Alice in Wonderland. Add to the mix a moody older brother, a crotchedy old grandpa, and ambitious parents. Oh, and a possible new boyfriend, whose father happens to be the chief of police. It's a great mystery, and although the reader has a pretty good idea of how it's going to end, Abrahams keeps us interested to the end by creating such a likable heroine in Ingrid.
Another great Young Adult mystery series is the Missing Persons series by M.E. Rabb. This is the story of two sisters who change their identities to escape their wicked stepmother. As a result, these two Jewish sisters from Brooklyn are now two Gentile sisters in Indiana. They become involved with the local PI, and help solve mysteries while avoiding being discovered. Great characters and location along with interesting stories make this a good series.