‘A tangle of scholarly findings’ on the one hand, and ‘some general remarks typical of school textbooks’ (9) on the other — this, in the opinion of Szymon Olszaniec, is the current state of research into the praetorian prefectures, the largest administrative units in the Roman Empire in the fourth and fifth centuries a.d. O.’s study aims to fill this perceived lacuna.

The first part of the book (‘The Establishment of the Office of PPO for Italy and its Structure’ (15–131)) traces the origin and evolution of the Prefect's office from the Tetrarchy. O. consistently rejects the views, of which he gives a thorough account, held by Jones and Chastagnol (regional prefectures were established in the 330s), by Seeck and Vogler (the 340s or 350s), and by Barnes (between the 330s and 360s). O. modifies the opinion expressed by Porena (who suggests 325/26–328), claiming that the process of establishing regional prefectures was completed earlier, in 324 or shortly after. Key to O.’s case, is a passage from the sixth-century bureaucrat and antiquarian, John Lydus (Mag. 2.10) which indicates that Constantine established a new prefecture in the East, adding it to the four existing prefectures in Africa, Gaul, Illyricum and Italy. Lydus also notes that the emperor, having lost Moesia and Scythia, moved to Asia Minor troops that had up until then operated north of the Danube. These events took place in 323 (the invasion of Moesia and Thrace) and in 324 (the redeployment of troops from the Danube). For O., this offers a coherent picture of Constantine's administrative policy: first seizing control of Licinius' territory and then reorganizing its administration (30–5). The account of John Lydus also matches the pattern of prefectures recorded on inscriptions found at Tubernuk, near Carthage (AE 1925, 72), Aïn-Rchine (AE 1981, 878) and Antioch (AE 1985, 823). In O.’s view, the unified prefecture of Italy, Illyricum and Africa was established under Constantine's three sons, when the number of prefectures was reduced from five to three — ‘this is when the Italian prefecture with a territory corresponding to that occupied by Constans’ state was born’ (38). Sometime after 324 (at a date difficult to pinpoint) the Prefects rose to the rank of clarissimi, and from 372 on they held the highest senatorial rank of illustres. O. does not see any significant changes in the officium of the Prefect until the beginning of the fifth century (only two new offices are mentioned: adiutor and numerarius). Prefects in Italy were originally based in Sirmium, then Milan and (from the late fourth century) in Ravenna (83–9).

The second part of the book deals with the powers and prerogatives of the Prefect of Italy (107–273). For O., the Prefect's legal, administrative and judicial duties formed the substantial core of his remit. O. examines the operation of the imperial postal system (cursus publicus). He supports the view (canvassed by Delmaire) that the Prefect was entrusted with the task of administering the postal infrastructure, while the magister officiorum was responsible for controlling postal services and especially for overseeing the issuing of permits (126–44).

O. also usefully surveys the Prefect's financial responsibilities: the Prefect drew up an annual budget, oversaw the collection of taxes, granted tax exemptions and supervised the collection of the annona and its distribution among the officials and the army. O. argues that susceptores and exactores performed similar tax-collecting functions (Seeck had suggested that exactores were only concerned with arrears) (152–63). O. also stresses the rôle of the Prefect in Rome's grain supply system (a rôle that has usually been associated with the Urban Prefect of Rome). A detailed analysis of the imperial legislation supports O.’s conclusion that the Prefect controlled the process of collecting the grain, its transport to Rome and its warehousing. He also supervised the sale of bread (177–8).

The Prefect determined the amount of taxes paid in cash and bullion and supervised their collection; he was also in control of extraordinary taxation and of tax exemptions granted to the Church. O. notes that the fiscal duties discharged by the Prefect of Italy overlapped with the prerogatives of the comes sacrae largitionum and the comes rei privatae. With service on the city councils becoming less and less popular, the Prefect also had to ensure that those who were obligated to serve as councillors did not evade their responsibilities. He also oversaw the process of granting exemptions. Alongside provincial governors, O. emphasizes the Prefect's close involvement with the running of city councils (234–48).

In his conclusion, O. again examines the rôle of the Prefect of Italy in the administrative structure of the Empire, focusing especially on his relations with lower-ranking officials — governors of provinces and dioceses. For O., there was no clearly defined hierarchy underlying the administrative system of the late Roman Empire. These officials were not direct subordinates, but rather they co-operated with the Prefect and his duties.

In sum, O. offers a comprehensive account of often lengthy scholarly discussions, convincingly correcting or questioning older views and offering new ones in their stead. His work, polemical in character, has a clear historiographical dimension. But it also offers a thorough analysis of all the important aspects of the operation of the Prefecture, as well as a number of closely connected issues (tax collection, cursus publicus, the position of the urban élites). O. has given us an interesting book that provides detailed information about the way the Roman Empire worked; it is required reading for all students and scholars of late Roman administration.