The United Nations on Monday released an authoritative report on North Korea that said the country is committing human rights violations “without any parallel in the contemporary world.”

U.N. investigators said they had sent Kim Jong Un, the North’s supreme leader, a letter putting him on notice that he is potentially responsible for aiding crimes against humanity.

The report notes that North Korea neither cooperated with the investigation nor allowed panel members access to the communist-ruled country.

Kim didn’t respond to the letter.

“He would not have a dialogue with us,” said Michael Kirby, head of the three-member U.N. panel that spent a year investigating abuses in the country.

The report makes for a devastating read, laying out the way North Korea conducts surveillance on its citizens, bans them from travel, discriminates against them based on supposed ideological impurities, tortures them, and sometimes banishes them to isolated prison camps, where they are held incommunicado.

“Their families are not even informed of their fate if they die,” the report said.

Although the commission’s report has no legal bearing, it recommended that the International Criminal Court (ICC) in The Hague take up the case against North Korea.

North Korea’s diplomatic mission in Geneva rejected the report, saying it was an “instrument of a political plot aimed at sabotaging the socialist system,” the Reuters news agency reported.

Here are four takeaways from the report and its 372-page addendum:

1. China might not support additional steps against the North, limiting the report ’s impact.

Kirby and the other commissioners had wanted to visit China, the North’s traditional ally. They wanted to meet Chinese officials and spend time near the border with the North, where Chinese authorities apprehend and repatriate North Koreans who escape. In a letter to the commission, China seemed to defend the North, saying it is “opposed [to] the politicization” of any country’s human rights issues.

If the ICC is to take up the case, the U.N. Security Council must approve the move. But China has a permanent seat on the council — and veto power.

Kirby said at a news conference in Geneva that the initial signals from China were “not particularly positive.”

2. What North Korea is doing isn’t genocide — at least, not quite.

The commission estimated that “hundreds of thousands” have been killed in North Korea’s gulags since the 1950s. But genocide, though it involves mass death, is a technical term, involving extermination along national, ethnic, racial or religious lines.

North Korea’s extermination isn’t quite that; the government tends to target people for their beliefs.

Kirby, a former Australian judge, reasoned this wasn’t the time to make a case for declaring genocide. The notion of crimes against humanity, the report says, is severe enough.

3. Even if we’ve long known the basics about North Korea’s abuses, the stories and details bring them to life.

The U.N. panel interviewed more than 320 people: witnesses, survivors and experts. The report itself is just 36 pages, but an addendum based on those interviews is loaded with specifics.

In discussing the secretive gulags, the report says that camp authorities have “received orders to kill all prisoners in case of an armed conflict or revolution so as to destroy the primary evidence of the camps’ existence.” The report says that the initial command seems to have been given by Kim Il Sung, the founder of communist North Korea, and that the order was reaffirmed by his son, Kim Jong Il, who succeeded him and was the father of the current leader.

A former prison guard who defected to the South, Ahn Myong-chol, testified that guards have been told to “wipe out” all inmates and “eliminate any evidence” if war or revolution breaks out.

The report continues, “Ahn and other witnesses also explained that specific plans exist on how to implement the order and that drills were held on how to kill large numbers of prisoners in a short period of time.”

4. The report tells North Korea how to change.

North Korea has so resisted major change that few ever talk about what reform would look like. But the U.N. report lays out some practical — and dramatic — steps. North Korea, the report says, should “undertake profound political and institutional reforms without delay,” such as placing checks and balances on Kim’s power. It should set up an independent judiciary and dismantle its state security arms, and it should release all political prisoners. It should reform its criminal code and abolish “anti-state” and “anti-people” crimes. It should allow people to practice religion. And it should establish independent newspapers.