The concept is straightforward. The team compressed a thin, curved elastic shell using forces on each end, and then made indents with a basic stylus (similar to how you print a conventional braille book). Once you remove the compression, the shell 'remembers' the indents. You can erase them just by stretching the shell. It sounds simple, but it's incredibly flexible: in its tests, Harvard could control the number, position and chronological order of the indents. There's no lattice holding it up, and it works with everything from conventional paper to super-thin graphene.
This is still rudimentary. While you can store memories in the shells, you can't perform computing tasks with them. You'd need a more sophisticated platform to control page changes. If that happens, though, braille books could be considerably more accessible. That could be helpful for long trips where you're searching for something to read, but it might also be incredibly valuable for schools that could easily send braille literature home with students.
Bottom image credit: L. Mahadevan/Harvard SEAS