Strong layout is a cross between fluid and fixed layouts intended to achieve intrinsic responsiveness according to the user device and viewport settings.
It is in resolves several issues of the older file based e-book systems while also maintaining contextual formatting in a progressive way to render content that scales (stretches or shrinks) responsively. Scaling is kept elastic on purpose to allow for maximum occupancy of the available real estate that is above the fold.
In general a strong layout is one where the proportions and the aspect ratios of content remains firm as the viewport is scaled. Individual items retain their visual balance and compositional/visual integrity no matter which device the book is viewed on. More or less like printing on an elastic Spandex.
An immediate side-effect of strong layouts is page-wise referential accessibility and numerical pagination:
Since a Superbook lives and scales on web, all readers around the planet get to see the same content on a given page number. People don’t have to worry about the file format, device compatibility, underlying tech or the software required to be to view the book properly. No specialized (and proprietary) hardware is required either.
One—a reader like me gets to know the page number my friends are on and two—everyone can finally be on the same page—so there are fewer disagreements.