A Sticky Situation — Abie Longstaff

The first book in The Trapdoor Mysteries, a series about Tally, a code-breaking, animal-loving servant girl and her best friend, a squirrel named Squill, who solve mysteries with the help of a secret library... Ten-year-old Tally is a servant girl at Mollett Manor. She sleeps in the scullery sink, and spends her days scrubbing, polishing and ironing (when she's not secretly reading books). Then Tally and her squirrel friend, Squill, find a secret library hidden under the manor - a magical library where the books come to life! When Mollett Manor is burgled, can Tally use the knowledge she finds in the books to catch the criminals? Can they even help her solve the mystery of her missing mother?