I went to google to view prior covers of The Bell Jar, and noticed that tons of past covers have been every bit as dumb and irrelevant as this one. Perhaps I should speculate on what each cover is trying to suggest about the book:
Note the dead rose. This book must be hell of dark. Incidentally, my favorite cover.
The scandal-making cover. This book is about a glamorous girl having an affair or something. Also, the 60s.
Obviously, this book is about craziness, because circles.
This book is about an exciting trip to New York!