In 2008 John W. O'Malley raised the question: What happened at Vatican II? In response, Mauro Velati provides an excellent historical account of one of the most fascinating yet neglected accomplishments of Vatican II: the unprecedented involvement of non-Catholic participants. Velati's theologically attentive story is told from the perspective of non-Catholics whose presence represented a vital foretaste of the ecumenical synodality that the Council itself had hoped to achieve. Velati argues that the decisive turn toward Christian unity during this time would not have been achieved without the presence of this non-Catholic remnant. He supports his account with extensive archival work from France, Italy, the Vatican City, UK, USA, Belgium, Switzerland, Germany and the Netherlands. Velati conducted his research under the guidance of Guiseppe Alberigo and in collaboration with members of the Fondazione per le scienze religiose Giovanni xxiii in Bologna, such as Alberto Melloni and Massimo Faggioli. Velati provides a detailed yet very readable account of the process and organisation of inviting Protestant and Orthodox observers to the Council. He notes that the unfortunate label ‘separated brethren’ was intended to mitigate suspicion by communicating that ‘the presence of the observers would not in any way indicate an openness to negotiations between the churches nor would it be used in a propagandistic sense by the Catholic Church’ (p. 83). However, Velati's argument is that these ‘separated brethren’ made important contributions to the Council itself. For instance, Velati is perhaps one of the only scholars to have documented the extent to which George Lindbeck acted in a representative role for Protestants with his contributions in the proceedings. Velati also notes how Jesse Bader (the delegate from the Disciples of Christ) raised the issue of gender at the Council: ‘No woman has been present in any of the Council's proceedings, nor has a woman's voice been heard on any subject under discussion. How different it is in most of our Protestant churches' (p. 183 n. 154). Moreover, Velati's account provides a glimpse into the unique character of Italian Protestantism with interventions by Waldensian theologians like Vittorio Subilia and Valdo Vinay, who channelled Karl Barth's admonition: ‘the way to unity of the Church can only be the way of her renewal. But renewal means repentance. And repentance means turning about: not the turning of those others, but one's own turning’ (p. 220). Besides responding to the core documents of Vatican II, Velati also describes the role that non-Catholic delegates played regarding the opening of bilateral dialogues, the debate about schema xiii, and the cancellation of the excommunication of 1054, thus shedding new light upon the post-conciliar transition with new ecclesial relations. Separati ma fratelli is truly a remarkable achievement that helps readers to gain a better understanding of the history and development of ecumenism through the microcosm of the non-Catholic delegation at Vatican II. Velati makes an original contribution to scholarship on the scope and ongoing reception of Vatican II by telling a hopeful story for Italian readers that should be translated for Anglophone scholarship. Research libraries and scholars of ecumenism should add this volume to their collections.