I read Stealing the Show by Ann Evans quite recently and I loved it all. One of the series of Little Tyke Murder Mysteries, this should appeal to middle grade readers. The author even allows the reader a chance to work out who committed the crime before revealing the answer to the mystery at the end of the book.
Emma and Lucy experience the chance of a lifetime. Emma has won a competition to spend the weekend with the hottest new boy-band around, Street Wise. She and her friend, Lucy, fly to France on the band's private jet, watching the concerts, going backstage. It all sounds brilliant, and it is. Until something deadly happens - and soon the girls are in danger.
Available from Amazon.