I just finished Christian Davenport’s book, “The Space Barons,” in which he writes about the billionaire tech guys whose obsession with space and rockets has changed the business from one run by a government monopoly (NASA) to an industry in which private companies are developing the newest technology to push humankind’s ascent further and faster.

The book’s two central figures are Elon Musk and Jeff Bezos, but it also includes stories about Richard Branson and Paul Allen, as well as maverick aeronautics engineer Burt Rutan. All of them cooperated with Davenport’s research on the book, although it took him several years to get Bezos to agree to talk. That’s ironic because Bezos owns The Washington Post, where Davenport covers the space and defense industries. Since founding Blue Origin, his space company, Bezos has been very secretive about what he and his team work on, but he finally opened up and shared at least part of the story with Davenport.

Musk, of course, is the exact opposite, making all sorts of proclamations both in person and via social media, some of which get him in trouble. But there’s no denying that his SpaceX has been the leader in the field, with regular launches of crewless cargo ships to the International Space Station. He also talks regularly about taking humanity to Mars, a mission he envisions beginning in just the next few years. Much of what Musk says can be interpreted as prideful boasting, but considering what he’s accomplished up until now, I wouldn’t bet against him in the long term.

Business people like these, already disruptors in other industries, have changed going to space from a project undertaken exclusively by nations to one being advanced by private companies that are pushing the envelope. They’re also doing it for a lot less money than the government usually spends (in some cases, a tenth the cost of contracts to traditional federal contractors like Boeing and Lockheed Martin, who have no interest in saving money because it all goes to their bottom line).

Next year will mark the 50th anniversary of the first men on the moon, and the 47th anniversary of the last, Gene Cernan. As he lifted off from the lunar surface, Cernan said, “We leave as we came, and God willing, we shall return, with peace and hope for all mankind.” As someone who grew up in the Mercury-Gemini-Apollo years and has always been fascinated with both the science and the adventure, it saddens me that no human has since set foot on Earth’s only natural satellite.

NASA has been stuck in neutral (or reverse) ever since the Challenger and Columbia accidents, with a long list of failed or unfinished plans to move humans beyond Earth’s orbit. If Musk, or Bezos, or anyone else can change that and create a new reality up there, they’ll deserve all the accolades we can afford them.

Astronaut Scott Kelly and others have said, “Space is hard.” Davenport’s “The Space Barons” tells the story of the billionaires — and the people who work for them — who are out to prove that it is not impossible.