The Case of the Missing Marquess by Nancy Springer, published by Philomel Books, a division of Penguin Young Readers Group, 2006.
Told in first-person, this novel shares the story of Sherlock Holmes' younger sister, Enola Holmes. I was impressed with the clever use of corsets and bustles to conceal large sums of money. I was also intrigued by the complex emotions the protagonist has regarding her older brother, the famous detective. She yearns for his approval, but his dismissive attitude angers her. This historical piece will resonate with young feminist readers.
This is the first book in the Enola Holmes series, and the fifth in the series, The Case of the Cryptic Crinoline was just released last month. Perfect summer reading for a young sleuth.