With The Princeling of Nanjing – the ninth instalment in his well-loved mystery series featuring globe-trotting accountant Ava Lee – Ian Hamilton continues to face down the largest problem confronting writers of successful series: his own success. Genre series, mysteries in particular, often fall into the rut of readerly expectation; with every subsequent book, their authors are forced into repeating the formula that brought them their initial acclaim, and the rut grows deeper and deeper. But like the best series writers – Ian Rankin and Peter Robinson come to mind – Hamilton manages to avoid that pitfall and keep the Ava Lee books fresh. He accomplishes this by acknowledging the elements that initially attracted Lee’s voracious fans, while simultaneously shifting the overarching narrative to force the character – and the reader – into fresh terrain.

The Princeling of Nanjing begins with a fashion show. It’s less than a year after the death of Uncle – Lee’s partner and mentor, an enigmatic former Triad leader – and five months after the events of Hamilton’s last book, The King of Shanghai, which saw Lee embarking on a business partnership of her own, the Three Sisters investment firm, and being drawn into the dangerous world of Triad succession.

The fashion show is the first fruit of Three Sisters, an over-the-top fete to launch the Po line of designer clothes. Before she can savour it, Lee is visited by Xu, the dynamic young Triad leader who, along with Uncle, tried to move the Triads away from drugs and prostitution into less unsavoury – though still illegal – pursuits, like pirating technology from the West. Lee’s relationship with Xu developed in the last book, with the Triad leader referring to her as mei mei (little sister).

As one might expect, Xu is in trouble with a powerful and corrupt political dynasty (including the titular princeling), which is pressuring him to return the Triads to their old ways, this time manufacturing and selling synthetic drugs. Lee begins to explore the finances of the family, in hope of finding something – anything – that can be used to take the pressure off Xu. What she finds, though … well, that would be telling.

That’s part of the sheer pleasure of the Ava Lee novels: readers know exactly what to expect, but Hamilton throws enough curveballs to keep them curious and involved. The Princeling of Nanjing has the familiar structures (the deepening intricacies of accounting and slowly unveiling conspiracies) and tropes (yes, we still get to know exactly what Lee is wearing at all times, and how she packs, two stylistic tics that have gone from distractingly repetitious to satisfyingly ridiculous), while the pressures and stakes of the narratives have shifted and broadened.

The result is a compulsive read, a page-turner of the old school. The ending may seem slightly muted, especially in comparison to the last novel, but overall, The Princeling of Nanjing is a welcome return of an old favourite, and bodes well for future books.