Jean-Claude Zeltner's Pages d'histoire du Kanem : pays tchadien is required reading for anyone interested in the history of Kanem-Borno. Focusing on the region of Kanem and only touching upon the Sayfawa in relation to Kanem after their relocation to Borno, Zeltner brings to the table experience with Arabic-speaking groups in the Lake Chad Region. So, the second half of the text basically consists of an overview of Kanem after the campaigns of Idris Alooma, with more detailed chapters on the migration of various Arabs like the Awlad Sulayman into the region. Perhaps the most detailed chapters are Zeltner's attempt at using the chronicles of Ahmad b. Furtu to give a breakdown of what exactly was happening in Kanem during the period from the late 1500s until the French conquest. As for his sources, Zelter relies on the usual ones: external Arabic geographies and chronicles from the medieval period, Ahmad B. Furtu, oral traditions, and the reports of European travelers and colonial officers, particularly Heinrich Barth and Gustav Nachtigal.
In terms of his 20th century contemporaries, Zeltner perhaps wisely draws heavily from Dierk Lange. Indeed, much of his study of the so-called Duguwa dynasty and early Sayfawa period is based on Lange's study of the Diwan. Like Lange, he creatively draws upon some of the same Arabic sources, but seems to borrow Lange's interpretation of the Sayfawa dynasty as a new one of Berber origins. Unfortunately, the evidence for such an assertion, based on our known written sources, is very slim. Zeltner seems to think the fact that Muslim Berbers were present in nearby Kawar by the 9th century, that the Halle manuscript of the Diwan separates Humme and his descendants from the earlier children of Duku, Selma Abd al-Jalil being distinguished as the first "black" king, and the matrilineal aspects of the Diwan establish a Berber origin of the Sayfawa dynasty. Such a perspective is unfounded based on our limited sources for early Kanem. Particularly when all the external Arabic sources allude to "Black" Kanem and do not mention "Berbers" in the ruling class class of Kanem.
Indeed, Ibn Sa'id, the main source on Kanem under Dunama Dibbalemi from the 13th century, clearly wrote about his "pagan" ancestors and their previous capital at Manan. All the evidence actually suggests, to our perspective, continuity from the "black" Duguwa to the Sayfawa. Nevertheless, the Diwan does appear to be a mostly reliable document on the chronology of Sayfawa rulers that can be corroborated by other sources. Particularly so if one ignores the legendary or semi-legendary earlier rulers of Kanem given fantastical reign lengths to connect the dynasty to Sayf. Therefore, one can understand why Zeltner was persuaded by Lange's analysis of it, and both tried to use it to elucidate the shift from the "Zaghawa" of the "Duguwa" dynasty to the allegedly "Berber" Sayfawa dynasty beginning with Humme in the late 11th century.
However, one must tread cautiously with some of Zeltner's (and Lange's) speculations on Kanem. For instance, Zelter sees in Dunama Dibbalemi the first king to truly break with pre-Islamic customs. Thus, the opening of the mune that is remembered in later sources as disastrous, was part of his Islamic piety and devotion. However, later Borno sources stress the Islamic aspects of the mune relic, particularly Ahmad b. Furtu in the 16th century and a late Sayfawa prince, Muhammad Yanbu. According to Yanbu, the opening of the mune was actually un-Islamic, while Ahmad b. Furtu equated the mune with the Ark of the Covenant. If true, then the Lange/Zeltner interpretation of Dunama Dibbalemi, as remembered in Borno traditions, cannot be accurate or adequate for understanding this first "historic" king of the dynasty.
The reality may have been far more complex in terms of the Islamization of Kanem and how the Sayfawa dynasty's relationship with Islam and Muslim legitimacy shifted over time. Moreover, our limited sources for early Kanem make it difficult to reconstruct social structures and relations. So, what exactly did the society of Sayfawa Kanem look like is nearly impossible to discern with certainty. We know of a large military, alliances with nomadic groups, vassal or tributary states, raids on "pagans" to the south of Lake Chad, the agricultural basis of society, the significance of the slave trade, dynastic feuds, Kanem's intervention in the Fezzan, royal pilgrimages, the migration of Arabic-speaking Judham into the region by the late 14th century, and the rise of the Bulala in Kanem. But the history of the Sayfawa dynasty, as limited as many of our sources are, provide little details on the rest of society. Based on the sources, Zelter wisely avoids unfounded speculation on the social history or other aspects of the region in the Middle Ages.
In summation, one can see why Zelter is required on the Kanem-Borno syllabus. His work continues the history of Kanem after the campaigns of Idris Alooma while also building on the scholarship of Lange to furnish additional data on the migration of Arabs into the region. Zeltner also includes the Middle Eastern and North African past of these Arab groups to contextualize the Lake Chad Region into a larger Islamic history that reaches back to the days of the Prophet. Lamentably, textual sources on Kanem for much of the 17th and 18th centuries are unknown or lost, so archaeologists and future scholars may one day uncover new materials to fill in the gaps of our knowledge. For example, how exactly did the Bulala eventually lose power in Kanem? When did Borno begin appointing the Dala Afuno in Maw, the capital of Kanem? In 1642 or perhaps later? How was Kanem part of Borno's relations with lands further east, such as Wadai, Darfur, the Funj, and Egypt? One would think Kanem continued to play a major role for travelers, pilgrims, and traders leaving Borno from the northern side of Lake Chad? One hopes future scholars can discover more about Kanem in later periods.