mentioned before, I'll be starting with this book because of nostalgia.
A Pattern of Blood follows Libertus as he's sent to investigate an attack on a decurion named Quintus Ulpius (which he coincidentally witnessed while looking for his wife). Unfortunately, Quintus is successfully murdered before Libertus can even talk to him. Libertus's patron Marcus is convinced he knows who the murderer is, but Libertus isn't convinced. And so, he starts investigating.
This was a really fun murder mystery, if the word fun is even appropriate. I enjoyed following Libertus about as he investigated, and reading about how he manages to persuade people to give him information, or twist his patron around so that he gets more time to investigate.
Plus, like a proper mystery, the identity of the murderer is deduced, not found out when the 'detective' 'accidentally' stumbles into something that oh-so-conveniently reveals the identity of the murder (I'm looking at you, ending of If Books Could Kill (Link needed), and all the other books like you).
While this book is set in the time of ancient Rome, the place is Corinium (modern Cirencester). So it's technically in the UK. There are lots of references to how this isn't like Rome, but all that talk of togas had me thinking in terms of the Colosseum and hot weather, which I'm guessing is quite far off the mark. That's what my brain gets for jumping to conclusions.
In conclusion, I really liked this book. From the foreword, it appears that the author has taken pains to be as accurate as possible. I liked how the setting pulled me into another world, and I enjoyed the mystery as well.