[I received a copy of this book through NetGalley, in exchange for an honest review.]
3 stars. The Library-verse and the main characters are now established, and the plot could therefore fulfil its course without much exposition. (Although the “negative” point here is that I don't think reading “The masked City” without having read “The Invisible Library” would be a good decision... but then, that's why it's called a second volume in a series, after all—exactly what it says on the tin.)
The focus is placed more on Irene herself, as an agent of the Library who has to navigate strange lands without counting on anyone but herself, nor on anyone's wits but her own. Kai isn't with her for most of the story, for reasons that are obvious from chapter 1: he's been kidnapped, and in a reverse Damsel In Distress plot, it's up to her to save him, with limited help from Vale who, as a human, would likely get mad very quickly in a high chaos level world.
And deliciously trope-y this book is, in more ways than one, both using archetypes and turning them around. The Dark Seductress, the Cunning Spouse/Grey Eminence, the Spy Hero(ine), the Enemies-turned-allies... Irene has to deal with those, and more, as the Fae in this universe are notorious for living vicariously through stories and archetypes, embroiling everybody around in their schemes in order to repeat those very plots. The more powerful the Fae, of course, the more gripping and unavoidable the story.
There's less of the Library itself this time, and more of the Librarian In Action: this can be good or bad, depending on what wishes to read—I admit I would've preferred to see more of the Library and other agents, even though in general I enjoy adventures and spies characters. The Language is a powerful tool when used well, which is shown several times, as Irene can basically bend reality itself, and turn antagonists around by crafting a Story of her own; and yet it doesn't make her all-powerful, because any circumstances when she cannot speak render her powerless—something she has to constantly keep at the back of her mind, in order to avoid such circumstances.
On the other hand, while there are high stakes and a real danger of war that must be averted, the kidnapping plot wasn't the strongest one ever. And while keeping Vale as a secondary character was great (I like myself a good old private investigator), not seeing him much was a bit of a letdown. Another thing, perhaps a corollary of the archetype/stories-driven atmosphere, was that it wasn't always easy to determine whether a particular action or decision was genuine, determined by the “storylines” Irene & al. Were thrown in, or an easy device to have the characters go where the author wanted them to. It both fits and doesn't, if that makes sense. (And I'm not quite sure what to make of the potential romance subplot. It's difficult to tell whether Irene is interested in either Kai or Vale in a "genuine" way—romance and love triangles can be pretty good or pretty bad, and can swing so easily from one part of the spectrum to the other...)
The writing felt also heavy-handed at times, laden with adverbs that kept creeping in. To be honest, I mostly read this novel while on the move, and as such I didn't pay as much attention as I could have to the style itself; however, I suspect that if I noticed this in such conditions, it may be, indeed, rather noticeable in general.
Conclusion: a fun story, with a good deal of action and plenty of nice little tricks for those who enjoy their tropes. Nevertheless, it lacked the spark the Library would have brought it for me (not enough books and book-related heists, I guess).