Where Tongues of Serpents was more getting Laurence to the point where he would finally go 'fuck it' and live to his own ethics rather than those expected of him by 19th century Britain, in Crucible of Gold actual plot stuff happens. The old 'visit a foreign place and see how it integrates dragons' formula is in place here, with the power-switch of dragons benevolently ruling humans in the Incan Empire providing an nice twist on it.
The interplay of dragons and humans is always been this series strong point, and there's a lot of fun with it in this one, with Iskierkia's determination to marry Granby into Incan royalty, and then Granby finally putting his foot down with her. And I was so happy at the reappearance of Lethabo and Kefentse when the third act suddenly gets back to the Napoleonic wars.
All and all a positive return to form.