This has always been one of my favorite books on the subject, and I am glad to see it reissued. O'Collins is a master of the subject matter, he writes very well, and every page has at least one useful insight that you can commit to memory or mull over. His Christology is biblical/Nicene/Chalcedonian (if you don't know what that is, you will love this book), and while he doesn't deviate from that position, he is fully engaged in the historical and modern challenges to Orthodox Christology.
You can use the look inside function to get the general idea of his plot. It flows perfectly as a book, but each section can stand alone for easy reference. After reading this book you will have:
1. a very strong introduction, really much more than a mere introduction, to the main points of the New Testament,
2. a clear grasp of the covenant that is fulfilled in Christ,
3. an understanding how the followers of Jesus understood him to be both the Christ (Messiah) and God, while remaining monotheistic,
4. a handle on how the early Church hashed out theological differences, approaches and trends while maintaining faithfulness to the tradition handed down to them,
5. an appreciation for how later Christians grappled with new challenges to the identity of God in Christ,
6. an understanding of why some modern approaches to Christ fall short,
7. a renewed faith in the reasonableness of the Gospel on historical, biblical and logical grounds.
While not meant to be an apologetic per se, the text can function this way easily. It is a solid piece of scholarship and, to me, the main book to have on hand when thinking about the issues.
Other books of interest may include: The God of the Gospel of John is excellent and one of the best books on scripture that I have read, Christ in Eastern Christian Thought by Meyendorff is concise and a needed corrective to the overlooked East (O'Collins does not overlook them, happily), Lord Jesus Christ: Devotion to Jesus in Earliest Christianity is a massive tome, but incredibly useful, Christus Victor: An Historical Study of the Three Main Types of the Idea of the Atonement (Spck Classics) shows how the dominant Medieval Roman/Protestant Christology needs some historical corrective, Cross of the Son of God is an irreplaceable collection of essays, Behr's The Mystery of Christ: Life in Death reminds us to be biblical in our minds and hearts, and Pelikan's Jesus Through the Centuries: His Place in the History of Culture is a very compelling survey by THE master historian of dogma.