The best approach would be to read it from start to finish, to see how it unfolds as a story (that’s biblical theology). And then also, once I’ve done that, it would be good to dip in and out of it in different places to concentrate on particular themes (that would be systematic theology). But to make sense of the “micro,” the details, we really need to get to grips with the “macro,” the overarching story of the whole book—the way the story unfolds, chapter by chapter, with each chapter building on the one before, revealing more and more about character and plot.
The word Bible comes from the Greek word biblia, meaning “books.” What you hold in your hands when you hold a Bible is a library: a collection of documents.
But we shouldn’t make the mistake of thinking that this “library” is a random grab-bag or, as we say on my side of the pond, a hotch-potch. The books hang together as a whole. They’re more like single episodes in a sixty-six-episode TV season, with each “episode” developing and expanding and deepening the overall story line. The Bible as a whole has many, many themes that run all the way through it, all the way from Genesis to Revelation.
That is what biblical theology is all about: tracing those themes across the timeline of Scripture as a whole, to see how they develop.
Biblical theology is often contrasted with systematic theology. At the risk of oversimplifying, systematic theology is like reading an encyclopedia, and biblical theology is like reading a story. The first takes individual subjects—for example, “salvation”—and tries to summarize everything Scripture says on the subject. But biblical theology traces the theme of salvation as it grows and develops across Scripture from start to finish. Biblical theology recognizes that Scripture itself is not an encyclopedia. It is a story, a true story, played out across the stage of human history. Like any story, it has a beginning, a middle, and an end, and we won’t be able to understand the story as a whole if we don’t attend to all those pieces, in sequence.
Like any good story, although the biblical narrative involves many different characters, there is a hero at the heart of it all, and the story, ultimately, is about Him. Jesus Himself is clear about this when He says that all of Scripture “bears witness about me.”