The Mysterious Mr. Badman is a bit unusual, featuring an amateur detective who is usually a carpet manufacturer (as the introduction from the series’ editor says, surely the only amateur detective to have that profession), and who is a kind older man, though backed up by a young nephew and a young woman who is involved in the case. Though it’s billed as a “bibliomystery”, honestly the book doesn’t play a huge part. It might as well be a second-hand suitcase or jacket, for all the book itself matters.
All the same, I found it fun: it was a quick read, and Athelstan Digby and Jim are rather sweet and careful in trying to sort things out and avoid scandal. Private justice, of course, but Digby in particular does his best not to cause lasting harm (padding a poker, for example, so as to knock someone out rather than crack their head open, even when he’s being imprisoned).
I wouldn’t say it particularly stands out among all the British Library Crime Classics, but it was exactly what I want from this series: a classic mystery, where all is resolved at the end, and the world goes back to normal.