Book excerpt: This is the fourth edition of the Yearbook on the African Union (YBAU). The YBAU is first and foremost an academic project that provides an in-depth evaluation and analysis of the institution, its processes, and its engagements. Despite the increased agency in recent years of the African Union in general, and the AU Commission in particular, little is known – outside expert policy or niche academic circles – about the Union’s activities. This is the gap the Yearbook on the African Union wants to systematically address. It seeks to be a reference point for in-depth research, evidence-based policy-making and decision-making. Contributors are Ndubuisi Christian Ani, Kwesi Aning, Juliana Abena Appiah, Habibu Yaya Bappah, Bruce Byiers, Annie Barbara Hazviyemurwi Chikwanha, Dawit Yohannes Wondemagegnehu, Debela Fituma, Cheryl Hendricks, Jens Herpolsheimer, Benedikt Kamski, Tony Karbo, Hubert Kinkoh, Klara Leithäuser, Edefe Ojomo, Francis Onditi, Naila Salihu, Rahel W. Sebhatu, Moussa Soumahoro, Elsie Tachie-Menson, Tim Zajontz.