The grid is a promise
When someone asks us to «break the grid» to make a page more interesting, we ask which promise they want to break. Because that's what a grid is: the part of the design the reader learns without noticing, which lets them stop looking at the structure and look at the content.
Break it, yes; but from the inside
A good exception stands out because the rest is regular. A page with ten exceptions has none. That's why we design the boring rhythm first, the one that delivers, and only then decide where and why an image deserves to leave the rails.
The reader doesn't see the grid. They see that the page treats them with respect.
— Sors
This holds for a website, a catalogue or a deck alike. The unit changes, the idea doesn't: everything where it'll be looked for next time.