It took me a few Anne Perry and Victoria Thompson novels to discover that the term 'mystery' has changed from how it was used let's say 10 to 20 years ago. Most readers might still associated a mystery novel with a puzzle and with sleuthing, but those terms rarely apply anymore to modern mysteries. Anne Perry is one of many contemporary authors who writes historical fiction with a romantic inclination, which is probably a better label than mystery. Granted, the reader does not know until the very end who has committed the heinous crime, but then again the reveal is most of the time arrived at by the culprit confessing without provocation and regularly without convincing motivation. You could say: with enough time and social pressure the murderer will eventually show him or herself without the need for evidence. Rarely in these novels is there actual hard evidence linking the crime to the crimee.
Traditionally in the context of a murder mystery there are a number of suspects each with the appropriate motivation as to why they wanted to snuff the life out of the poor victim. At the end of the story a sleuth or consulting detective explains why only one of the suspects could have actually committed the crime and why the rest of the bunch are not eligible for the title of murderer, no matter how much they desired that tribute.
In an Anne Perry novel the mechanism is reversed, we now have a number of suspects each of which was potentially at the proper place (one will never know) with the right intentions and correct means, but physical evidence and eyewitness reports don't matter that much. The one who has the best motive wins, it's that simple. Instead of the traditional plotting of the author, sleuthing by the detective and puzzling by the readers, we now have novels where the mystery content revolves around veiled dramatic character interactions. Most of these interactions will mostly appeal only to female audiences and ironically portray a rather traditional domestic picture and gender role division.
From a historical perspective there is much to be found and experienced. Authors like Anne Perry, Victoria Thompson and Caleb Carr to name just a few, are heavily invested in accurate depictions and appropriately original detail. Reading an Anne Perry is just as much an immersive trip into Victorian Times as it is an ongoing daytime television saga. Readers aren't really invested in an Anne Perry for the story, but for the endless almost but not quite amorous interactions between Charlotte and Thomas. For a Victoria Thompson novel you can swap out Frank and Sarah, everything else stays the same.
If you like a trip into a complete and convincing Victorian world with lots of interesting drama and elaborate character interactions through dialog, then you're in for a treat. If you're looking for an Agatha Christie mystery then I suggest you read an Agatha Christie.