Sorry, all look like some error appear at time add book.
And now for you error go at time not remove book - these error go at time remove Product - what was created base on that book.
And also it may go from time when you created Product - for book. By defausl exist only English language pack - so and product will create for that pack
Best if you will write to us at support form with admin access to yours site and we will check where error.