It is written by two people who build interfaces rather than two designers who write: every rule comes with a before and an after drawn next to it. The structure runs from the general — how to start, hierarchy, spacing, type, colour, depth, images — down to the details, and each item fits on two pages.
What I took from it
Starting from one concrete feature instead of the page template. A screen is designed by solving the first thing someone will do on it; the frame, the menu and the footer come later, or not at all. That changed the order in which I build a view or a report: the column the person came to look at goes first.
Cutting the options up front. A fixed scale of sizes and spacings, a short list of shades defined before starting, and the argument about twelve versus fourteen pixels disappears. Consistency does not come from taste, it comes from having fewer choices.
And the rule I use most: make something stand out by turning down what surrounds it. On a screen where everything shouts, the fix is almost never to enlarge the important thing; it is to take weight off the rest. It works the same in a document as in an interface.
What I left out
The chapters on images and shadows, which solve consumer-product problems rather than working-screen problems. And a warning about scope: this is interface design, not content and not conversion. A screen can look immaculate and still fail to say what it is for. For that you need to read something else.