For me, the most intriguing part of the book describes Thatcher's life after leaving Number 10. Politically-speaking, she was dead in the water - there is no role in the British constitution for an unemployed prime minister. But Campbell is astute enough to highlight the human aspects of her new situation. Only days earlier, she was being feted by President Mitterrand at Versailles. Now, shorn of the Downing Street machine, she had difficulty even using the telephone to find a plumber. Thatcher's refusal to adapt to her new situation caused her successor much grief, and the book relates the despair which John Major felt at her off-stage sniping , especially when he was trying to rebuild bridges to Britain's European partners.

Having already documented the lives of two former Prime Ministers -- David Lloyd George and Edward Heath -- Campbell is able to view the Thatcher years with a historical perspective. The conclusion of this book, however, is disappointing. A work of this magnitude deserves a resounding finale, but instead it runs into the sand, offering little more than a couple of pages to sum up Thatcher's impact. It's not a bad ending, but I feel that the author could have done justice to the rest of the book by bringing together more effectively the various strands of Thatcher's life.

That said, The Iron Lady is a masterpiece of political biography, meticulously researched and written in an enviable style that both informs and entertains. It may be too soon to call it the definitive biography of Britain's first woman prime minister, but the next time an author sets out to write Margaret Thatcher's premiership, this is the first book they should open.