Murder in the Telephone Exchange by June Wright

First published in 1948, when it was the best-selling mystery of the year in the author's native Australia, Murder in the Telephone Exchange stars feisty young operator Maggie Byrnes. When one of her more unpopular colleagues is murdered -- her head bashed in with a "buttinsky," a piece of equipment used to listen in on phone calls -- Maggie resolves to turn sleuth. Some of her coworkers are acting strangely, and Maggie is convinced she has a better chance of figuring out who is responsible for the killing than the rather stolid police team assigned to the case, who seem to think she herself might have had something to do with it. But then one of her friends is murdered too, and it looks like Maggie might be next. Narrated with verve and wit, this is a whodunit in the tradition of Dorothy L. Sayers and Josephine Tey, by turns entertaining and suspenseful, and building to a gripping climax.