Schaff, Philip. History of the Christian Church (The Complete Eight Volumes in One). Amazon Kindle Edition, 2014.
Volume 2, Ante-Nicene Christianity A.D. 100-325, “Chapter 13. Ecclesiastical Literature of the Ante-Nicene Age, and Biographical Sketches of the Church Fathers.” sec. 159-204.
§ 200. Novatian.
After a fairly extensive bibliography Schaff identifies Novatian as "the second Roman anti-Pope" (Schaff 2014, loc. 23406, par. 2), a figure who resembles Hippolytus as well as Tertullian. It is significant that his writing shows skillful use of Latin. Schaff rather incidentally observes that the Roman church at this time, mid 3rd century, "may have amounted perhaps to about 50,000 members" (Schaff 2014, loc. 23412, par. 3). Though we don't know specific birth or death dates, the dated correspondence of Novatian is in 250-251.
In Novatian's time, the majority elected Cornelius as pope, but a minority elected Novatian as anti-Pope and he was consecrated before being denounced and excommunicated (Schaff 2014, loc. 23425, par. 6). The schism spread, between followers of Novatian and his strict view of discipline and others, who were more lenient. At issue were "the extent of the power of the Keys and the claims of justice to the purity of the church and of mercy towards the fallen" (Schaff 2014, loc. 23431, par. 7).
Schaff lists numerous written works of Novatian, two of which have survived. "The most important is his Liber de Trinitate (31 chs.) composed A.D. 256" (Schaff 2014, loc. 23431, par. 8).