A Kindle doesn't look much like a book, it looks more like a tablet computer. The only similarity is a rectangular area of text, which is the bare essence of a tool used for reading, also present in the Kindle web app and street signs.

The floppy disk is not the predecessor of the save button; they existed together for many years and the button image persists because it is a familiar way to represent an abstract concept.

I don't know anything about architecture, and when I read this article I searched my phone for pictures of buildings and found one that showed the row of small blocks along a top edge.

These are called dentils because they resemble teeth.

The Roman architect Vitruvius (iv. 2) states that the dentil represents the end of a rafter (asser). It occurs in its most pronounced form in the Ionic temples of Asia Minor, the Lycian tombs and the porticoes and tombs of Persia, where it clearly represents the reproduction in stone of timber construction.

I think they look nice, and it's interesting that they are now decorative elements with an atavistic function, like the non-closing shutters on the front of my house.