It might be a bit daunting that a book claiming to contain What Christians Should Believe approaches 500 pages. Protestant evangelicals have grown accustomed to reductionist theology in which "the essentials" are listed by bullet point and presented as the complete Gospel. In fact, the entire Bible contains the Gospel, and for each point there's depth and nuance.
After all, we're talking about God. To suggest that everything we "need" to know about Him fits in one paragraph, or that the real meat of Scripture is all morality and human guidebook, is dangerously close to blasphemy. God didn't write the Bible primarily for its human readers—He wrote it to reveal Himself rationally and comprehensibly.
Which provides the model for Driscoll and Breshears, who attempt in Doctrine: What Christians Should Believe to clearly identify and explore the true essentials of the Christian faith. This isn't one of those fun intros to theology that spends more time telling cute stories or elaborate illustrations than investigating deep spiritual matters.
The text is accessible (you don't need a B.A. to understand it), and it engages tough, sometimes literally impossible-to-understand concepts, honestly and skillfully. Using the flow of the biblical narrative as a framework, the authors work through the doctrine of the Trinity, revelation, God's image, the Fall, the Covenant, resurrection, the Church, the Kingdom, etc.
There are problems with the text. The most obvious is the lack of a clear section devoted to pneumatology, the study of the doctrine of the Holy Spirit. Perhaps this is due to Driscoll's more charismatic leanings coming into conflict with Breshears' more conservative stance. Whatever the case, this is a serious oversight and deficiency in a book that purports to teach what Christians need to know about the faith once for all delivered to the saints.
This isn't late-night-by-the-fire reading. While it isn't a textbook, it is a manual of sorts, providing an exploration of the historical borders of orthodox Protestant Christianity. Because it's focus is God, Doctrine makes superb devotional reading, though you might want to read more than a page a day. Highly recommended for laymen, students, theology buffs and neophytes alike.