If you're anything like me this doesn't sound riveting, although perhaps the subtitle (An exposition in Father-Son theology) is slightly more appealing. When I heard Harold at a local conference this was not his only topic - I was particularly interested in his take on economics today based on the Bible. Still. this was his main message, and a year later, I was still curious and had saved enough to afford it. I then spent most of the next year grappling with it.
When I heard him talk what most impressed me was the development of this systematic theology. Since becoming a Christian in my late teens, I'd heard plenty of Bible teaching, but still had many questions. He started (using pen and paper only) to list what the Bible said about a topic. And the next. and the next. He then reviewed each topic, and when he found discrepancies, made revisions.
This doesn't mean it is the final "truth". Near the end of the third (last) volume, he mentions that another teacher (Tom Wright) has a different interpretation of a relatively minor point. Today this may seem unusual, given how often people are so often afraid to express differences, but in the quest for truth, to think that one person has all truth is at best arrogant. Even the foreword says this is unlikely to settle all differences
Having said that, and having eventually conceded that this aligns more consistently with "truth" than the traditional "theology" I picked up through a couple of decades of church attendance, at least I can now back away from discussions where traditional theology is accepted as "truth" and engage more discerningly with more open discussions. Of course, the danger of changing my mind is being open to deception - but the same could be said of always holding to the same views.
A lot of my views were already being tugged in new directions, and that was not comfortable for me. However, the consistency of his overall approach has been key.