Marius Maximus or 'Ignotus'?
Certain scholars have always defended the value of specific parts of the work. Anthony Birley has argued, for instance, that the lives up to Septimius Severus are based on the now-lost biographies of Marius Maximus, which were written as a sequel to Suetonius' Lives of the Twelve Caesars. As a result, his translation of the History for Penguin Books covers only the first half, and was published as Lives of the Later Caesars, Birley himself supplying biographies of Nerva and Trajan (these are not part of the original texts, which begin with Hadrian).
His view (part of a tradition that goes back to J. J. Müller, who advanced Marius's claims as early as 1870) was vigorously contested by Syme, who held that virtually all the identifiable citations from Marius Maximus are more or less frivolous interpolations into the main narrative source, which he postulated was a different author whom he styled 'Ignotus ("the unknown one"), the good biographer'. He argued that as far as is known Marius did not write a biography of Lucius Verus, even though the biography of that prince in the History is mainly of good quality, and that 'Ignotus' only went up to Caracalla, as is revealed by the lamentable biography of Macrinus.
Read more about this topic: Augustan History