Reform of the Liturgy: 1948-1975 - By Archbishop Annibale Bugnini. This is a comprehensive work in which Bugnini explains in detail the approach taken to reforming the Mass, Breviary and Ritual after Vatican 2, including while he was Secretary of the Congregation for Divine Worship. He is surprisingly candid about his intentions to go beyond what was required by Vatican 2 in fundamentally changing the liturgy, admitting that he was even keen to change the Rosary! He explains in detail how rushed the work was, and their strategies for convincing the Holy Father and the bishop consultors to accept the changes.
Liturgicae InstaurationesInstruction of the Sacred Congregation for Divine Worship on the orderly carrying out of the Constitution on the Liturgy, September 3, 1970.
Congregation for Divine Worship