Universe-traversing Librarian Irene Adler and her assistant the dragon prince  Kai return in The Masked City, second in The Invisible Library series following the titular volume in the series. After settling themselves in the Quasi Victorian world of airships, Fey nobles and derring-do, Irene’s life is, if not precisely stable and uneventful, at least predictable. Find rare books for the library in this alternate London, dodge machinations of local villains, spar with her bête noire, and get into adventure after adventure. Routine, right? Second novels, especially following on high-concept hot ideas like the interdimensional traveling library and librarians of Cogman’s series, are tricky. How do you keep the material fresh? How do you avoid the temptation to “do bigger, and more” as a easier substitution for the harder tricks of building on worldbuilding without making it unstable or unpalatable, and developing characters and their arcs in interesting and meaningful ways? The second novel in such writing is harder than the first, and for me as a reader, with the baseline established, I am looking for that growth and development, and read for it.