X-raying a Book
X-raying a book is Adler's metaphor for seeing the hidden structure beneath the surface prose. A worthwhile book has a skeleton: a unity, major parts, and an order among those parts. The reader's job is to find it.
The practical expression of this is twofold. First, state the unity of the book in one sentence or a short paragraph. Second, outline its major parts and show how they hang together. If you cannot do that, Adler assumes you do not yet really know what the book is about.
This concept matters because many reading failures are structural failures. Readers remember local passages but miss the architecture that gives them meaning. X-raying a book fixes that by treating structure as part of comprehension, not as optional study decoration.
It pairs naturally with inspectional reading, which often provides the first rough map, and with analytical reading, which sharpens that map into a more exact outline.