It must be lonely being Jean Kennedy Smith. At 88 she is the sole survivor of the most remarkable family in American history, the Kennedys.

The former ambassador to Ireland had lost none of her wit and wisdom the last time I met her, which was quite recently at an Irish Consulate event in New York. She seemed as bright and spry as ever, but it must weigh heavily on her that she is the last of  a truly remarkable family who have all now slipped into the shade.

Rarely did a family embody so much of the American dream as the Kennedy’s of poor Irish farming stock did.

That is why her new book "The Nine of Us: Growing Up Kennedy" is so important.  It is the last eyewitness account from within the family of some of the most famous figures in America.

There is Jack, the future president, Robert, the lost leader, Teddy the great legislator; it goes on and on.

It is the Kennedy parents who continue to fascinate, though. The book’s most interesting part to me will be about them. As the daughter or Rose and Joe Kennedy, two incredibly strong figures who wielded power in different ways, Jean must have wonderful insights.

Joe Senior was the Irish kid who disturbed the universe, joining elite society and groups that intensely disliked the Irish but were won over by Joe’s charm and, not coincidentally, his money.

He triumphed on Wall Street, raised a president and two U.S. senators, a war hero, an ambassador, a founder of the Special Olympics and a beloved daughter, Kick, who died during the war.

The shadow over both parents, however, is the mentally ill Rosemary, who, in 1941 at the age of 23, underwent a frontal lobotomy, a barbarous procedure that somehow had become the preferred mental treatment at the time.

The episode is clouded in mystery.  Various reports say Rose knew little about it, that Joe just went and had it done because mental illness at the time was a huge stigma. Others believe Rose initiated it.

Read more: Jean Kennedy on the family and legacy that changed America

Whoever was responsible, it did not for a minute stop Joe in his career. He became ambassador to Britain, a job traditionally reserved for blue bloods and royal fanciers of whom there were many in high positions in America. The grandson of a poor potato farmer who fled the Famine now had come back to Britain as America’s plenipotentiary in a time of war.

Joe’s major public mistake was opposing that war, failing to see what Hitler was really likely to do and agreeing with appeasement. That stance essentially ended his Washington career and earned him Roosevelt’s enmity.

But he had other careers such as Hollywood. He loved hanging around with famous actresses such as Gloria Swanson (who ended up with six husbands). He was incredibly unfaithful to Rose, who bore it with a stolid Irish forbearance perhaps because her own father, Honey Fitz, was a philanderer too.

In Rose, Joe met his match, though she wielded power differently.  She was the custodian of the kids, the person who developed them, spent time with them and instilled in them a deep sense of her own rigid Catholic values.

There is one anecdote that stands out – the time when Cardinal Eugenio Pacelli, later Pope Pius XII, came to visit.  Rose had a plaque placed on the couch where he sat.

Rose took frequent trips on to Europe and elsewhere to get away from her philandering husband. When he had the stroke that left him incapacitated she had the final say, and he became agitated in her presence.

It seems America can never get enough of the Kennedys with new books all the time. Jean Kennedy’s one will stand out, of course, as an eyewitness and participant in history. It is sure to be a bestseller.

Read more: Rosemary Kennedy’s tragic life story will be told in film starring Emma Stone