It explores the issues arising from the attempt by Lothar II, king of Lotharingia (855–869), to rid himself of his wife Teutberga and replace her with his concubine, Waldrada.
Divorce had not been an issue prior to this, and so this offers a unique insight into changing attitudes at the time, specifically in relation to the growing influence of the Catholic Church over marriage.
The letters appealed to Hincmar for advice regarding the high-profile attempt by King Lothar II to put aside his wife, Teutberga, in the hopes of marrying his mistress, Waldralda.
Hincmar of Rheims (d.822) De divortio Lotharii regis et Theutberga reginae is a lengthy treatise that explores the issues of Lothar II's divorce through a series of questions and responses.
A recent edition is that of L. Böhringer, De Divortio Lotharii Regis et Theutbergae Reginae (1992) in the Monumenta Germaniae Historica series.
It has since been retranslated with accompanying commentary by Rachel Stone and Charles West, The Divorce of King Lothar and Queen Theutberga: Hincmar of Rheims's De Divortio in 2016, published by the Manchester University Press.