Published by Scholastic
Summary: Cleo and Evan miss their favorite school librarian, Mrs. Hilliard. After she mysteriously disappeared, the strange Ms. Crowley took over. One day, Ms. Crowley is acting odder than ever. The two kids follow her, and discover a secret underground library. They find a note from Mrs. Hilliard telling them she’s trapped in a book, and they need to solve the mysteries in the other books to free her and avoid getting stuck themselves. Entering one of the books, they find themselves in 19th century London, where they help a teenage Sherlock Holmes-like detective figure out who stole a diamond from a wealthy family. Ms. Crowley makes an appearance in this mystery, and after it’s solved, the three of them return to their school. More mysteries await, however, as they work to free Mrs. Hilliard. 128 pages; grades 2-4.
Pros: The mystery was surprisingly good, with a cast of suspicious characters and a bumbling, yet charming detective. The story-within-the-story structure is a fun way to move the series along.
Cons: The beginning was a little slow.