The Case of the Missing Marquess: an Enola Holmes Mystery, by Nancy Springer
IndieBound Description: When Enola Holmes, sister to the detective Sherlock Holmes, discovers her mother has disappeared, she quickly embarks on a journey to London in search of her. But nothing can prepare her for what awaits. Because when she arrives, she finds herself involved in the kidnapping of a young marquess, fleeing murderous villains, and trying to elude her shrewd older brothers--all while attempting to piece together clues to her mother's strange disappearance. Amid all the mayhem, will Enola be able to decode the necessary clues and find her mother?
My Thoughts: Oh, I love Enola Holmes! I am addicted to the whole series and if you read this one you will be too! These books are just a tiny bit older than most of the other books I recommend (not a lot though), mainly because this contains real thrills of murderous villains, etc--but that's the fun too!