I read this review too and, even though I disliked MT intensely, I didn't believe that she could be as unpleasant in her personal life as she was in her political one. I was wrong. It can't be said that these disclosures are untrue because most of them are in the letters to her sister. Particularly shocking was the extremely snobbish and racist remark about "tatty tourists, Jews and the nouveau riche", and her attitude towards her bereaved father, with whom, apparently, she had little contact in later years.
I have also caught a bit of the official biography of MT in the morning on Radio 4. She certainly doesn't come across as a character one could warm to. In the extracts I've heard, she seems totally self-absorbed. Her sister must have been very tolerant to put up with endless details of MT's academic, social and political triumphs, her obsession with her appearance and with the financial status of her male companions.