I've just finished re-reading the seventh section of Louis Berkhof's Principles of Biblical Interpretation on "Theological Interpretation." I can't recommend these 33 pages enough. Much of what is taught here I've had to struggle toward slowly on my own - it would've been great if someone would've drilled these ideas into my head in seminary or elsewhere.
The first two requirements of biblical interpretation are historical and grammatical, but the third "must" of theological interpretation is consistently ignored or unhelpfully assumed (and therefore hidden from scrutiny). Berkhof, though, asserts that purposefully and openly pursuing theological interpretation is to "refuse to place [the Bible] on a level with other books," since the Bible is an organic whole, has a Divine Author, and is intrinsically theological.
While I don't agree 100% with Berkhof's conclusions on when prophetic language is literal or figurative (I think he fails to adequately address Hebrew parallelism of thought - sometimes parallelism is the tool that shows something to be a figure rather than an explicit statement introducing a figure), almost all of the rest of this material is well-organized, adequately defended, abundantly illustrated from Scripture, and is irreplaceable in its value for the student of biblical interpretation.
If I had to strip my library down to what I could fit in a backpack, this book would make the cut (and not just because it's small!).