In the Chinese system of writing, when another ‘wood’ is added to one ‘wood’, the word signifies ‘forest’. If you add another ‘wood’ on top of ‘forest’, it becomes ‘deep forest’.
In the case of the word ‘book’, a stroke is applied to the bottom of the stem of ‘wood’ to represent the logging of trees to make books. And when ‘tree tops’ are cut with a stroke applied on top, it symbolizes the end of the world…