Confusing book, that ironically has the subject on interfaces - something that almost by definition should convey information as clearly as possible. Confusion

Confusing book, that ironically has the subject on interfaces - something that almost by definition should convey information as clearly as possible. Confusion as the title of the book, why do we interface? evolves to a perhaps more interesting: why do we design? but it then leaves that question unanswered. Then is goes on to explain the alphabet and I bounced.