The ant in the sentence "this" in the book "This is really happy" refers to the word that can walk in the book. The Ant in the Book mainly tells the story of a small ant crushed by a book clip, which leads the characters in the book to form an endless story.

These stories include rabbits' carrots, dung beetles' love for circles, bears in the library, mice in the rose villa, the maze of moles, a nest of birds in kangaroo bags, ants sending them around and so on. The author describes them with warm humanistic atmosphere and gentle life. In this quiet reading, the spiritual life of minors has grown unconsciously.