[NiLuJe]

@jgoguen: Agreed. But in this specific instance, if we only strictly apply it to most-likely-unique stuff we're the ones adding, doesn't that alleviate that issue? While still addressing @GeoffR's concern of these new divs inheriting unwanted margin/padding-related properties?

(I'm starting to feel sympathy for people that actually do this kind of stuff for a living ^^).

EDIT: On the other hand, a quick test seems to be inconclusive as to whether !important actually 'helps' (in the sense avoiding inheriting margins), so, either I'm doing something wrong, or I'm still confused about how everything interacts with everything ^^.

EDIT: Scratch that, there was a third wrapping div in my test file, hence my confusion... -_-".

So, take two?:

div#book-columns {
        margin: 0;
        padding: 0;
}
div#book-inner {
        margin: 0;
}