Somewhat preposterous - and dealing in cliches before they were set - but somehow I liked it. I think it has to do with how certain characters came across - like Sarah Newman's tale, coming through in her notes, her testimony. Then, late in the book, there's the copper who thinks through a clue, determines what it really means. Aldridge manages to come across as the conscientious, and wronged, man who just wants people to hear what he believes.
In some ways, this "first detective novel" was ahead of its time; I especially like the way it patiently fills in all the pieces of its full story; it knew to tantalize for as long as possible.
In other ways, this book is way out of date. The Mystery content is premised on - what? - "fringe science", considered rather a stretch, on a few fronts, by this time...but not in the 1850s. You may end up doing that rolling-of-the-eyes thing. But you may also find you care about some of the supporting characters, especially when life is unfair to them - and there may be a slow build-up of "I really need to know...not so much who the killer is, but how it was done.".
Tentative 3.5 star rating - but it was strange pleasure to read it.