gistfile1.txt

    public int CompareTo(object obj)
        {
            if (obj is Book)
            {
                Book otherBook = (Book)obj;
                if (this.Title != otherBook.Title)
                {
                    return this.Title.CompareTo(otherBook.Title);
                }
            }
            else
                throw new ArgumentException("One or both objects are not books.");
        }