Promise Me, Dad is Joe Biden’s poignant account of the most challenging year of his vice-presidency and the second-most difficult year of his life.

The first time he had been knocked down by what he calls “the Irishness of life” was immediately after he was first elected senator from Delaware, in 1972. Less than six weeks later his wife and his daughter were killed and his two sons were injured in a car accident.

The second time came four decades later, when his son Beau, by then attorney general and likely next governor of Delaware, was found to have brain cancer.

Biden’s book describes a year of almost unbelievable sensory overload, when the vice-president was juggling frequent visits to the hospital to comfort his son with regular phone calls to the prime minister of Iraq and the president of the Ukraine, and a big initiative to stabilize Central America after thousands of children started to stream across the southern US border.

Folded into all of this activity was Biden’s struggle to decide whether he would try to succeed Barack Obama, or leave the contest for the Democratic presidential nomination to Hillary Clinton and Bernie Sanders.

We get a handful of surprising vignettes. There is Biden looking into Vladimir Putin’s eyes and saying “I don’t think you have a soul”, and the Russian president replying: “We understand each other.”

There is Obama telling Biden he doesn’t think he can beat Hillary, but also offering to loan him money when the vice-president says he may need to mortgage his house to raise funds to help his son.

And there is the vice-president making sure that each of his children and grandchildren visits a Nazi concentration camp, to give them a “visceral jolt” and to remind them that “this can happen again” and that “silence is complicity.”

The book is a reminder of the importance of politics: how much elections can change the trajectory of a country

More than anything else, the book is a reminder of the importance of politics: how much elections can change the trajectory of a country, and how different America has become one year after Donald Trump was elected president.

Here we have a portrait of two politicians, Obama and Biden, devoted to each other and to doing whatever they can to improve America and encourage democracy around the world. Instead of a president like Trump, in thrall to Putin, we watch these two lobbying European allies to engage in the sanctions they think are necessary to punish Russia for stealing Crimea.

And rather than tweets and press conferences giving aid and comfort to white supremacists, we see a vice-president visiting the Emanuel AME Church in Charleston, South Carolina twice in three days after nine of its parishioners were shot dead by a crazed racist – partly because Biden had known one of the victims, the Rev Clementa Pinckney.

Biden gives himself some well-deserved credit for the supreme court decision to make marriage equality the law of the land in 2015, partly because he came out in favor of that position before Obama did and partly because he played an important role in the effort to stop Robert Bork joining the court in 1987, when Biden was chairman of the Senate judiciary committee.

When Bork’s nomination failed, he was replaced by Anthony Kennedy, who was supported by Biden and who has written all of the important pro-gay decisions the court has rendered. The difference between Bork and Kennedy is perhaps the strongest evidence of all of the power of politics.

Biden repeatedly asserts that he would have been successful if he had run for president in 2016. But first his decision was delayed by his son’s cancer, and then it was made for him by his son’s death. Although Beau Biden had repeatedly urged his father to run, in the end he was just too drained by the tragedy to run for president.

The author explains that the grieving process “doesn’t respect or much care about things like filing deadlines or debates and primaries and caucuses. And I was still grieving.”

If his son hadn’t died, and if he had prevailed over Clinton in the primary, Biden would have campaigned for a $15-an-hour minimum wage, free tuition at public colleges, real job training, onsite affordable child care, equal pay for women, strengthening the Affordable Care Act and modernizing the country’s roads and bridges and water and sewer systems.

Would all that and his stronger connection to working-class Americans have combined to derail the Trump juggernaut?

That will always be one of the unanswerable mysteries of American politics.