A "riveting" mystery -- surely a joke on the part of the blurb writer, as the denouement revolved about rivets. A rivet is what holds a beam up, and in this case ... But I must not spoil the story.
An architect serves five years in prison because a balcony in a theatre he designed collapses, killing several people. I'm not sure that the conviction and punishment were convincing, but never mind, it was interesting to see England and London through the eyes of a man who had been shut away while amazing modern inventions were coming to life. The changes he saw -- motor cars, street lighting, films -- were intriguing, and his wonderment felt real.
The writing style reminded me of H.E. Bates and J.B. Priestley, both favourite authors when I was a child. Dated, but being so dated suited the early twentieth century setting. The careful descriptions of theatre life and theatrical performers was very much in the Priestley ("The Good Companions") mode.
I could have done without the long descriptions of the strange English class system, which surely everyone knows about already, even if they don't watch English TV dramas like "Downton Abbey". The descriptions of painting flats for the theatre, and the building of great theatres and so forth were more interesting -- but again, rather too much of it. The research outweighed the mystery to such an extent that the mystery didn't matter any more. By the time I got my way to the end, I honestly didn't care who did it, or why.
But if you are interested in learning about early twentieth century theatres and architecture, go for it. It's easier to read than a textbook. But don't expect too much of the plot.