My father and I just finished The Book Smugglers, Book Four of Anna James' Pages & Co. series.
The British Underlibrary may be saved, but there are other plots (so to speak), and other evils in the bookwandering world that were but hinted at before and now come by postage in the form of a poisoned copy of the The Wizard of Oz. But now it is Milo Bolt who drives both story and the magical train Sesquipedalian alongside his friend Tilly in a hunt to find the poisoner and save their families, questing from the Emerald City to the canals of Venice. Along the way unraveling and finding mysteries not written in any book as the circumstances around Milo's life and family are revealed to be bound like book a power struggle between one who takes the phrase "knowledge is power" to obscene lengths and another whom might just be trustworthy. We will found out soon enough, for it is Milo and Alessia's story now. All aboard the Quip!