It's been a good month for me to find established series reaching new highs and this one in particular makes me very happy. I'm a reader, a reviewer and a collector; how could I not fall immediately in lust with the sheer idea of a secret library existing outside of space and time, whose librarians scour parallel worlds for unique editions to collect? It's a real wish-fulfilment series but, as much as I've enjoyed them, I've never felt entirely right with them thus far. They've traded on my wishes but tried too much or done too little. This book, finally, is the novel I've wanted from this series.

It's the fourth book and it takes a somewhat different direction from its predecessors. Irene and Kai are still our leads, but Peregrine Vale, the great detective of parallel world N-395, only shows up in a passing mention. The threat to the Library isn't an outrageous one from the arch-villainous ex-Librarian Alberich but a subtle one, an attack on its neutrality by hauling one of its members onto one of the two sides that battle around it. Therefore the mission, to quietly but emphatically dismiss that attack, makes complete sense. And we see what we really want to see, I think, which is Irene doing what she does best on a world that seems believable to us but also fits the structure of her universe.

Here's the background you need if you're coming in on book four. All these parallel worlds fit somewhere on a spectrum of order to chaos. Dragons, like Kai, are dominant on the high order worlds but the fae on high chaos worlds. In between, the battle between them rages and the Library stays out of it. This book highlights that the battles aren't restricted to being between the two non-human races, but can be fought within one of them. Here, it's the dragons, whose large multi-world kingdoms are divided into four inner ones and four outer. The Queen of the Southern Lands rules one of the outer ones and the retirement of Minister Zhao has opened up a position of some importance. There are only two candidates, Jin Zhi and Qing Song, and they've both ably met a set of challenges. The last one is to retrieve a book, a specific edition of the Chinese classic, 'Journey to the West', an edition that could only come from one specific world.

And so the game is afoot, as Peregrine Vale would no doubt say if he was here to say it. But, Jin Zhi arranges a meeting with Irene to point out that her competitor, Qing Song, has got a Librarian in his pocket, something of importance because it destroys the carefully preserved neutrality that the Library cultures. And so Irene, having reported this to the Library's internal Security department, is sent on an undercover mission to A-658 to figure out what's really going on and how much her colleague Evariste is involved. Oh, and stopping it. Quietly. And she has to do so without any official backing, because the Library is neutral. If she fails, the Library may have to deny all knowledge of her actions or, at the very least, hide her out for a couple of hundred years until it all blows over.

I liked this one a lot. I liked the set-up, which grounds the age-old conflict between dragons and fae in a more believable framework and focuses in on the dragons for a change. I liked Melusine, the no-nonsense Librarian working Security, who sets up Irene for her mission. I liked that mission, which actually feels acutely dangerous, unlike the more playful equivalent in 'The Masked City'. I especially liked A-658, on which Irene has to manoeuvre her way through an alternate Boston and New York that are stuck in the Jazz Age.

Everything is emphatically twenties, from the flappers to the tommy guns, from the speakeasies to the sobriety protestors, from the mobsters to the zoot suit that Kai wears to fit in. Author Genevieve Cogman kicks this into gear in style, having Irene and Kyle arrive in the ashes of the Boston Public Library, then arrested off the train to New York because the cops think she's a visiting crime boss from England, Jeanette Smith. Of course, they track down Evariste, as you might expect, just ahead of Qing Song, who's seeking him with the aid of wolves. Of course, the situation isn't as simple as they might have hoped and so begins the real story.

With Irene front and center, the mission grounded and A-658 conjured up with glorious texture, 'The Lost Plot' is easily the best of the four 'Invisible Library' books thus far. In fact, its successes helped to highlight the less successful aspects of the prior books for me. Irene is a highly capable leading lady, but she's diminished when the author emphasises Peregrine Vale. I do like him as a character and I thoroughly enjoyed his exploits in the first book, but I was surprised to find that I didn't miss him here at all. She's also lessened by Kai, because he's far from the worthy character she is. His best use thus far is to say or do the wrong things, so emphasising how Irene would have said or done them differently, but this book highlights how that really isn't needed. She's very able to stand on her own and get the job done and 'The Lost Plot' is better because she's allowed to do so.

While I've had problems with each of the prior books, I should emphasise that Cogman's prose has been a firm delight throughout. N-395's Victorian London always worked so well because she painted it so effectively, from the zeppelins in its skies to the werewolves in its tunnels. Similarly, A-658's Jazz Age New York works so well because she paints it just as effectively. The Prohibition era can't be much better than as summed up by her description of the bar at the Underground, a speakeasy run by local mobster Lucky George: 'the bottles behind it gleamed like a distant promise of heaven from the outskirts of hell.'

As long as Cogman continues the series the way she handled it here, foregoing the grand theatrics and focusing on believable details in the political structure of the universe she built, it's going to go from strength to strength. Maybe she'll find a way to keep Peregrine Vale active in some way without him taking over. She may well have found a way to put Kai to better use but I can't go into that without spoilers. Frankly, I wouldn't be disappointed if he vanished entirely and Irene picked up a new partner. We've met a few candidates for that position already and the troubled Evariste is easily another one.

Let's find out when book five hits the streets as it surely will. 'The Bookseller' reported back in early 2016 that books four and five had been bought by Pan Macmillan, so we have at least one more to go and, if it's anything like this one, they'll be snapping up books six and seven too. Watch this space. ~ Hal C F Astell

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