Propaedeutica ad sacram theologiam in usum scholarum, seu, Tractatus de ordine supernaturali Book

The previous gentleman to review this book gave a link to some spurious website concerning the heretical errors contained in this book. Unfortunately that website isn't the best source for determining the orthodox nature of a theological work. However, having said that, this book is very erudite if not dense, yet it is very fruitful. Also, this book is a series of essays written over a ten year period which concern fundamental theology. FT is a branch of theology in the Catholic Church whereby, as a discipline, seeks to muster together the different aspects of revelation and theology and clarify them for those inside the Church and for dialogue with those outside as well. Think of Fundamental Theology as both the State and Defense departments of the tradition of the Catholic Church. Ratzinger was a major contributor to it but it was 'founded' by Henri de Lubac in the mid-1930's. It is still developing and is in its nascent stages.

Some sections of the book to check out:

Part 1:
Tradition, anthropology of.
Baptism
Conversion-metanoia

Part 2:
Ecumenism with Protestantism and ecclesiology.
Sacramental theology including the priesthood as necessary mediator-relationship.

Part 3:
Experience as basis for any faith.
Science in relation to theology.

This book is a very nuanced work and can be dense, so I hope that these sections can be fruitful reads to encourage you to continue through the end.