Edited by Herbert Vorgrimler.
New York: Herder and Herder, 1967.
Originally written in German, this work was compiled immediately after the Council. It is particularly good at outlining the history of each document's composition. There are contributions by some of the most important theologians of the time, including Yves Congar, Bernhard Häring, Josef Jungmann, Karl Rahner, and Josef Ratzinger.
The volumes are all available online on the Internet Archive, a trusted source, but one for which it is necessary to create a free account and login:
(Sacrosanctum concilium, Inter mirifica, Lumen gentium, Orientalium ecclesiarum)
(Unitatis redintegratio, Christus Dominus, Perfectae caritatis, Optatam totius)
(Nostra aetate, Dei Verbum, Apostolicam actuositatem)
(Gravissimum educationis, Dignitatis humanae, Ad gentes. Presbyterorum ordinis)
(Gaudium et spes)