To put it simply, I loved this book. From the moment I picked it up, I didn't want to put it down. Though the mystery wasn't so much a mystery by the middle of the novel (I guessed the culprit, though perhaps Downie intended for us to get hints along the way and work this out), I still found how it unfolded very riveting. Also, Downie inserts a lot of humor into the novel and you end up feeling both sorry and amused by Ruso all in the same breath. Ruso is a very likable character because he is neither too unfortunate nor too impressive. In the end, Ruso comes out as an average man. Because Ruso was such an interesting and likable character, he sustained the story well enough for me when the plot waned.
What about historical accuracy? In the end notes, Downie herself admits that information about Roman Britain is hard to come by and scant. She also confesses that some of her information is made up or exaggerated to move the plot along. The few books that Downie listed as sources are secondary sources, which are always to be used critically since their information may not be correct or unbiased. A few primary sources would have made her history more credible, certainly. A lot of the speech and infrastructure in Medicus was inspired by modern practices- characters used words like 'lad' and 'bloody'. Still, I was relieved that this book did not read like a textbook and that it did not focus around big names and big people. Yes, Julius Caesar marching on Rome was an amazing thing, but we should only have so many fiction books about it. It is nice to read about an average Roman.
It was refreshing that Downie allowed me to use my own knowledge of Rome to fill in the gaps and set the scene rather than laying it all out for me in a tedious, fact rich way. Like I said, Medicus did not read like a textbook. In a way, it was taken for granted that the reader should know a little something about the Roman way of life. I may be better off than your average reader since I do know a lot about Rome to fill in blanks with. Yet, a non-scholar can still pick out a lot about Roman life such as that slaves were property and frequently abused, Romans wrote on wax covered pages with a stylus, Romans diluted their wine with water, etc. You won't finish this book without some idea of how Romans lived.