The popular Sister Fidelma mystery series is set in 7th-century Ireland and follows Sister Fidelma, an Irish nun who serves as a dalaigh (advocate/lawyer) in the Brehon Court of Ireland. Raised as an Eoghanacht princess, Sister Fidelma studied civil and criminal Brehon law. Her expertise often draws her into solving murders and other crimes. She is assisted in her investigations by Brother Eadulf, a Saxon monk.

Readers not only love Sister Fidelma herself but also appreciate the rich historical details of the period, which author Peter Tremayne, an expert in Celtic history, weaves into the stories. Many find the history as compelling as the mysteries themselves.

The novels delve into the unique roles of women in society, the complex political and religious conflicts of the time, and the diverse cultural landscapes across Western Europe during the Middle Ages, and the clashes in law and religion between Ireland and Rome.

Fans recommend starting the series from the beginning to be properly introduced to the characters and setting, follow the historical progression, and enjoy the personal journeys of Sister Fidelma and the supporting characters.