I've really enjoyed the first three books in this series, and though I enjoyed this one too it was a bit heavy on the sentimentality.
Penrose crafts her plots around fictionalised versions of real historic events, and this time around it's mathematical machines and financial shenanigans that may or may not involve the East India Company. Her historical knowledge always adds an extra depth to the story, and a well plotted mystery makes it even better.
Charlotte has built quite a scooby gang around her and Wrexford, and the characters are fully fleshed and they're easy to care about and cheer for. But the dynamic between Wrexford and Charlotte has become increasingly sentimental to the point of down right syrupy. The sentiments are lovely, but just a little too much for my tastes. I was also getting aggravated at the overuse of the word ‘dastards’.
I'm still a fan, but I'm hoping the next book will regain a little of the edge the first couple had.