One of the most thorough scholarly examinations of the 20th century changes in the Church.
Prof. Romano Amerio was an episcopal consultant to the Central Preparatory Commission of the Second Vatican Council, and a peritus present during the Council sessions. He was a friend of the late Cardinal Siri of Genoa and died in 1997.
This is his master tome - over 800 pages of exhaustive critique of the 20th century crisis, covering the conduct and documents of Vatican II, the priesthood, catechetics, religious orders, feminism, ecumenism, faith, morality, Catholic culture, liturgy, and more - from the time of John XXIII to 1985.
Over 800 pages, with multiple indices. Those looking for a "deep dive" on the subject matter will not be disappointed.