The history of Leo the Deacon is a classicizing history covering the period 959– 986. The text survives only in Parisinus Graecus 1712. It was written in the late tenth century; either after 989 or after 995, and most likely before 1000. It is organized into ten books. It begins in the reign of Romanos II, focusing on Nikephoros II Phokas's conquest of Crete and following Nikephoros's military career in detail. The murder of Nikephoros by John I Tzimiskes is narrated in affecting style at the end of book five. The second half of the history focuses on John's military career and ends with John's death by poison in 976.

In the prologue, the author describes himself as Leo, the son of Basil, born in the village of Kalo ë in western Anatolia. Elsewhere in the text he mentions that he pursued higher education in Constantinople and was ordained a deacon. He appears to have participated in the Bulgarian campaign of 986 and witnessed the Byzantine defeat in the battle of Trajan's Gate. There are no suggestions in the history that Leo lived beyond 1000. Leo also wrote an encomium to Emperor Basil.

Leo's history is noted for its revival of classical forms of history writing. He includes ostensibly verbatim speeches, digressions on natural phenomena, and occasionally marks time with references to the seasons. His level of detail in descriptions of military engagements is also reminiscent of some classical histories. In using the lives of the emperors Nikephoros II and John I as the primary structure, the history participates in the middle- Byzantine trend toward organizing history around imperial biographies.

Because Nikephoros II Phokas is the hero of the first half of the book and John I Tzimiskes is the hero of the second half, scholars have postulated that Leo used sources written from different viewpoints. Kazhdan has argued that Leo used a pro- Phokas source along with another source opposed to Constantine VII and Nikephoros II.