The long-delayed biopic “Gotti,” starring John Travolta as New York City Mafia boss John Gotti, opens in theaters Friday. Here, the Dapper Don’s son John “Junior” Gotti tells Dean Balsamini what he thinks of the film, which is based on his book “Shadow of My Father.”

Today is the 16th anniversary of my father’s passing. I was in Cannes, France, for the world premiere of “Gotti” in May. You have the subtitles across the screen, and it’s your book based on your life, and people are gauging your reaction. It’s not like you’re in your living room with a martini and a cigar. There are sensitive parts, such as when my brother gets hit by a car. I didn’t want to shed a tear. I had to fight it.

My big gripe? This project started out with the promise of being a three-hour, $70-million movie. In the end, the movie is 100 minutes long — and you really can’t capture a 600-page book in 100 minutes. It’s impossible. This should be a 10-part series. “Black Mass” [the 2015 blockbuster starring Johnny Depp as Boston gangster Whitey Bulger] came in with a budget of $53 million. This movie came in with a budget under $10 million . . . JT [Travolta] had to act the s–t out of this movie because there’s no exploding buildings or crashing airplanes. You even get the sense, in court scenes and bar scenes, that we were limited on extras.

Movies like “Donnie Brasco,” “Goodfellas” and “Black Mass” have much larger budgets and there’s room for mistakes. They just re-shoot until they get it right.

Kevin Connolly [best known for playing Eric on “Entourage”] directed this movie with a boot on his throat. The producers were constantly harassing him to keep it moving along. To his credit, he did a fine job. JT had to work on a high wire with no net. That’s why he’s one of the greatest actors of our time. He carried the movie on his shoulders.

In the beginning of the movie, John [Travolta] is on the promenade in Brooklyn Heights and he’s talking about life on the streets and how it usually ends one of two ways: dead or in jail. He’s wearing a gray overcoat — that’s my father’s actual coat. I also lent the filmmakers my father’s hankies and ties — he was partial to Leonard and Brioni — and Piaget watches and cuff links. John wanted to be as much into character as possible.

John was great, but it wasn’t perfect because nobody could have gotten it perfect. John did a better job than Armand Assante [in the 1996 film “Gotti”], and Armand did a good job. There are overreactions that weren’t my father’s personality. In one scene, I’m being introduced to him for the first time as a street guy [after being inducted into La Cosa Nostra] and they have him a little bit too overjoyed. It would have been a more serious, solemn moment for my father.

I thought John did a tremendous job looking like him, although JT is a lot taller and has different color eyes. Their builds are different. My dad was [5-foot-10], barrel-chested. JT doesn’t have my father’s natural swagger.

The hardest scenes to watch included my father’s final days in solitary confinement and the death of my brother Frankie, who was fatally struck by a car on March 18, 1980. In the movie, they have my mom laying on the couch with my two sisters crying. In real life, she was upstairs on tranquilizers. My mother was inconsolable.

Kelly Preston didn’t get a lot of screen time as my mom, but she did a solid job. She looked the part and captured my mom’s wit and combativeness. Spencer Lofranco, who portrays me, has a Canadian accent and doesn’t look like me.

When producers told me Stacy Keach was playing Neil Dellacroce [Gambino crime family under-boss and John Gotti’s mentor], I thought it was going to be a disaster — I remember him in Cheech and Chong’s “Up in Smoke.” But he absolutely nailed it. When he and JT are onscreen together, I thought I was watching John Gotti and Neil Dellacroce.

The only thing missing from this movie is that I would like to have seen Sammy Gravano [whose testimony put the elder Gotti in jail] die. [Gravano is, in fact, still alive.]

Some critics say this movie glorifies the mob. Really? Really? What part glorifies the mob? The loss of dear friends due to prison or murder? The fact that my father spent his last 10 years in solitary and died handcuffed to a bed? [John Gott died in 2002, aged 61, at the federal prison hospital in Springfield, Mo., while serving a life sentence without parole for racketeering-murder convictions.]

I’m a movie buff. My favorite of all time is “Spartacus.” On a scale of 0-10, I gave “Braveheart” an 11. I give “Gotti” a 7 because it’s not long enough for me. The 100-minute Hollywood formula is not appropriate for this story.