The book is written "from the inside", so to speak. That is, both authors are not only Roman Catholic, but also priests and theologians. Furthermore, both are Jesuits, that is, monks in the order of the Society of Jesus. Despite the widely held cultural belief that the Roman Catholic church is highly secretive if not downright dishonest, both O'Collins and Farrugia write openly: they note the various failures of the past. However, as they also note early on, the history of the Roman Catholic church is far more than one of failure: otherwise, the only thing that could account for its success would be the (manipulatory) work of the Holy Spirit.
The book has 11 chapters:
1: The First Thousand Years
2: The Second Thousand Years
3: Revelation, Tradition, and Scripture
4: The Tripersonal God and the Incarnate Son
5: The Human Condition
6: The Life of Grace and the Hope of Glory
7: The Sacraments
8: The Catholic Church and its Mission
9: Catholic Moral Life and Teaching
10: Basic Characteristics of Catholicism
11: Current Challenges
Hence, the book is far more than a simple history of the world's largest religion: it is an overview - at times, considerably detailed - of Catholic history, thought, and practice. As the last chapter's title indicates, the book also takes stock of the current state of things and looks toward the future.
Each chapter takes the historical development of ideas into account in the presentation of its theme and the authors note that there have been many changes over time, particularly with and since Vatican II, the most recent of the church's ecumenical councils. The authors show a good deal of sensitivity to both the Reformation (c. 1500 c.e.) and the Great Schism (1054 c.e.), which was when the church Catholic broke into eastern and western churches: the Orthodox and Roman Catholic churches, respectively. Although the authors show themselves to be sympathetic to the Anglican Communion and other Protestant groups - some of which are far more in continuity with the shared Catholic tradition than others - there is a special place given to the Orthodox church.
It is appreciated that this book does not take a "top-down" approach: the social life of the church, filled with saints (and sinners), philosophers and mystics is what really creates the history of the Roman Catholic church. The authors are particularly fond of Dante, interestingly enough, and quote him regularly.
The picture that they paint of the Papacy is one where the primacy of the pope emerged out of political need but also became more corrupt as time went on, culminating in the high middle ages and leading to the Protestant Reformation. The pope's power has been in decline since then, reaching its all time low when Napoleon conquered the Vatican. Since then, there has been a considerable amount of theological work done by various persons and councils so as to fully articulate the place of the pope in the life of the church, both preventing abuses of power but also keeping his position the prime position of leadership. O'Collins and Farrugia discuss the meaning of papal infallibility - developed in recent times - and its precedent in earlier trends and decisions. However, they note that papal infallibility does *not* mean everything a pope says is perfect or true. Rather, it means that *when* the pope claims to speak "ex cathedra" - "from the chair (of St. Peter)" - he is and will be correct. This has only happened *twice*, though. The pope is presented as a central figure in the Roman Catholic church - he is the central bishop - but not as more important than the larger, shared tradition of Roman Catholicism.
Particularly helpful at the end of the book is a list of titles for further reading, some of which I have bought and others which I am planning to buy. The detailed chapters are welcome to this reader; this book is no lightweight introduction. I think that cuts both ways, though, as the amount of detail - lovingly and painstakingly written about - may overwhelm some readers. Regardless, I think this book is still an excellent place to start learning about the Roman Catholic church.