Through a combination of bravery and naivete Nic ends up with a mark on his body that gives him magic powers. He is not an instant superhero however and his efforts are bumbling to put it mildly. He is motivated to free himself and his sister from slavery and seeks to do so with a laserlike focus, Nic is not alone however. As he tries to find his sister he meets two other people who befriend him. He and Aurelia don't hit it off immediately but gradually they grow on each other.
As you would imagine mythology and ancient history are integral parts of the story. One can hope that younger readers who may not have read these tales from antiquity would be inspired to do so after reading this book.
Not only does Nielsen paint a realistic picture of Rome at the time but she also conveys the instability that was a feature of life in the empire. Plots and counter plots galore are revealed throughout the story and it ends with one final stunning revelation that is a cliffhanger and a door into more books in the series. Mark of the Thief was a good read and I recommend it for ages 10+
You can check out this and other reviews on my blog here.