Swear to God was one of the first books I read as a Catholic. I was either going through the Rite of Christian Initiation (RCIA) or had just been initiated in the Church. I also audiobooked it from Audible. At the time, I didn't grasp the book fully, maybe because I couldn't see the words in front of me, but I did appreciate it. I have since decided to re-read it, a decade later and see how much more it speaks to me today.
The book begins with Dr. Hahn recounting his first encounter with sacraments in Protestant seminary. In a nutshell, they bored him. He was more interested in the Bible and preaching. Frankly, I could relate with him. To a Protestant, sacraments aren't that interesting or essential to salvation. Having now experienced multiple sacraments within the Church, I have come to realize years after my conversion just how interesting, essential, and crucial to our salvation they really are.
Dr. Hahn then takes the time to explain what a sacrament is, how many there are, what exactly each one is, and where they can be found in Scripture. Next, he devotes several chapters to covenants and covenant theology. In these chapters, he explains what covenants and oaths are, important covenants in the Bible, how covenants were crucial to Creation, how oaths were important to society.
This book is easily understood, because it is written in true Scott Hahn fashion. It is a nice mixture of Scripture, patristics, and personal experience. This is an excellent introduction to the sacraments and the power and importance they have in the lives of Catholics. I highly recommend it for both old and new Catholics. It makes the perfect gift for those in the RCIA program or just those who are showing a little bit of interest in the Catholic faith.