This is the best book by this author that I have read so far.
Perry's writing style is unobtrusive, somewhat given to unclear pronouns, but generally solid.
I found it interesting that nothing seemed to differ between this setting, in 1859, and the setting of the author's Pitt novels, in the late 19th century, except that the Pitts have telephones. I wonder how authentic that is. I found no obvious errors, except that, in keeping with the rest of Perry's books, the women seem very independent for the period.
Perry has come up with what must be one of the best characterization hooks ever invented. William Monk suffers from amnesia. He has reason to think he was an unpleasant person, a person capable of wronging others, in the past. But... he can never know what, exactly, he did. I would have liked to see a few more original touches in his *current* character, but it's still a fascinating idea.
The plot of Cain his Brother is outstanding. A minor consistency error here and there does not detract from its drama. A man has murdered his twin brother -- or has he? I thought I had the secret figured out several times, but I was wrong. But when the answer was revealed, it made perfect sense. Perry sometimes has surprise twists out of nowhere at the end of her books, but this time she got it exactly right. I remained unclear on one thing --Ravenstone's motivation -- but that may be my oversight.
This is a very entertaining historical mystery which I strongly recommend.