It turns out that building an interconnected cinematic world that is the setting for 23 movies is not as easy as Marvel Studios makes it look.

The Marvel Cinematic Universe emerged in 2008 with four simple words when Robert Downey Jr., in the guise of billionaire playboy Tony Stark, told the world, “I am Iron Man.” Almost a decade and a half later, Marvel Studios is the undisputed champion of comic-book-inspired cinema, a true Hollywood superpower with some of the highest-grossing films of all time.

But what is the origin story of the MCU?

It’s a secret that has been left to the imaginations of an ever-speculative fandom — until now.

“The Story of Marvel Studios: The Making of the Marvel Cinematic Universe,” by Tara Bennett and Paul Terry, documents events before and after the MCU’s Big Bang moment. The books (plural, there are two volumes), at more than 500 pages, feel like they could substitute for a kettlebell in a Chris Hemsworth-inspired weightlifting routine.

In January 2017, Bennett and Terry, both movie fanatics, were tapped by Marvel Studios to explore the possibility of chronicling the MCU’s first decade. Both had experience documenting pop culture moments, working on companion books and magazines about television shows, including “Alias” and “Lost.” Marvel gave the authors full access, from interviews with top brass to set visits and test screenings.

“The intimacy of involvement was the most we’ve ever had,” Bennett told The Washington Post. “This was deeply gratifying and surprising, in the best way.” She said the amount of time that they “were given by everybody” indicated how important the project was to Marvel Studios.

This may come as something of a shock to those who have been paying attention. Marvel is famous for its secrecy. So it was remarkable to have Marvel Studios President Kevin Feige, producers, art directors and actors talk candidly about the MCU. Most were old hands at hardly talking at all — or at talking without actually saying anything. The reticence was all a part of the no-spoiler culture. According to Bennett and Terry, some interviewees found the opportunity to talk about their work cathartic.

“Every interview was really wonderful in its candor, because, from creatives on down, it was like, ‘This is a Marvel book? And they want us to talk?’ ” Bennett said.

The two-volume set stretches from the 1990s, when Feige was working as an assistant to movie producer Lauren Shuler Donner, through the moment, in 2009, that Disney shelled out $4 billion and changed the course of Marvel Studios forever.

These days, Marvel’s success feels like a foregone conclusion, but Bennett and Terry delve into obstacles along the way.

For example, Marvel almost didn’t get the necessary approval to use the classic rock of Black Sabbath that is now synonymous with Iron Man films. But last-minute meetings to get corporate approval (i.e. to spend the money to secure the rights) saved the day.

Meanwhile, the negotiations with Sony to bring Spider-Man to the MCU in a shared capacity were tense. It wasn’t easy for Sony to relinquish its status as superhero-movie heavyweight champion, and the company wasn’t eager to accept that it needed help with one of the most popular superheroes of all time.

The books also answer questions that have nagged superfans. For instance, why didn’t admired filmmaker Edgar Wright direct the first of several Ant-Man movies after being attached to the project for so long? The MCU had become a sprawling, interconnected web, which wasn’t necessarily what Wright had originally signed up for, according to Bennett and Terry,

“I think MCU fans, as they read this book, as each chapter is laid out, year by year, the exponential risk-taking . . . you will feel it,” Terry said. “We felt it as we were telling the story.”

Just as Marvel had growing pains along the way, the development of the book was not without setbacks.

As Bennett and Terry were putting the finishing touches on their work in March 2020, the world shut down. And yet, the writers said the pause actually ended up benefiting their work.

“You’ve got to find your lemonade in everything, and the lemonade for us, with the pandemic shutting [everything] down, was it was literally the first time Marvel Studios had to stop,” Bennett said. “From the [first] Iron Man [movie] they have never stopped.”

Producers now had more time to search their phones, garages and files for MCU relics that likely would have remained in the dark had everyone at Marvel Studios not been able to come up for air after working straight through a decade.

“It was an absolute glorious cornucopia of extra material that we could get from photos, ephemera . . . personal emails . . . and all of that came from people having to stand down because the world stood down,” Bennett said. “And that was, for us, to the benefit of the book . . . to get an extra layer of participation and research . . . and all the goodies that came from that.”

David Betancourt writes about all aspects of comic book culture for The Washington Post.

The Story of Marvel Studios

The Making of the Marvel Cinematic Universe

By Tara Bennett and Paul Terry

Abrams. 512 pp. $150