Harriet Bean and the League of Cheats — Alexander McCall Smith

Harriet Bean loves nothing more than a good mystery. And together with her five extraordinary aunts (Veronica, Harmonica, Majolica, and twins Japonica and Thessalonika), she is always ready to take on a new case.

Harriet doesn't think twice when her mind-reading detective aunts Japonica and Thessalonika enlist her help in catching a cheat at the racetrack. After all, Harriet is just the right size to go undercover as a jockey. But when the plan takes an unexpected turn, Harriet finds herself in the saddle!