A horizontal expansion followed by a vertical contraction of a Microsoft Excell cell.
This book is made with Microsoft Excel.
It can be opened and read from both sides with varying results and titles.
In both cases cells evolve from thinnest possible lines to standard width squares and back to lines again, creating a zig-zag trace of movement.
In the middle of the book the expansion changes to a contraction and the zig-zag causes a 90-degree change in orientation.