The other is: Sarah Bradford's biography of Diana. (I also liked Ken Wharfe's memoir very much.)
Ms. Bedell-Smith digs deep and sometimes unsympathetically into the life of Diana, Princess of Wales. However, I think for the most part she is objective about Diana, not objectionable -- in other words, she tells Diana's story as it was, not as we might WISH it was. Diana had her bad points. She was self-absorbed at times; manipulative; involved her boys a little too much into her personal problems; impulsive. In some ways she hurt the Royal family, yet she also breathed new life into the old institution.
Ms. Bedell-Smith is also right on target about Diana's relationship with Dodi Fayed. It was a terrible step backward for her, and quite simply, her actions all during the month of August 1997 (with hindsight) clearly point to her confusion and unhappiness, instead of joy and confidence.