Here is some essential reading about the Traditional Mass.
The Traditional Mass: History, Form, and Theology of the Classical Roman Rite by Michael Fiedrowicz.
Nothing Superfluous: An Explanation of the Symbolism of the Rite of St. Gregory the Great by Fr. James W. Jackson
The Heresy of Formlessness: The Roman Liturgy and Its Enemy (Revised and Expanded Edition) by Martin Mosebach
Noble Beauty, Transcendent Holiness: Why the Modern Age Needs the Mass of Ages by Peter Kwasniewski
And in the matter of liturgy and liturgical reform…
The Spirit of the Liturgy by Joseph Ratzinger
The Reform of the Roman Liturgy: Its Problems and Background by Klaus Gamber
Turning Towards the Lord by Uwe Michael Lang
And because the priest’s self-understand is tied to everything in the Church…
In Sinu Iesu
The Day Is Now Far Spent by Robert Card. Sarah
God or Nothing: a conversation on Faith by Robert Card. Sarah
From the Depths of Our Hearts: Priesthood, Celibacy and the Crisis of the Catholic Church by Robert Card. Sarah and Benedict XVI