In one way, adapting Stephen King’s 2018 novel “The Outsider” into a 10-episode series for HBO was old hat for writer and producer Richard Price. He has adapted his own novels for screen in the past, as well as projects including “The Color of Money” and “The Night Of.” But in another, taking on this project allowed the veteran industry professional a chance to achieve a childhood dream.

“It’s this combination of a police procedural that takes this twist into the supernatural without ever quite leaving the police procedural world. The easiest thing for me to write is the police world and ever since I was a kid, I’d always wanted to write a ghost story,” he tells Variety.

“The Outsider” is an almost 600-page tome that starts out seeming like a regular detective novel (though if you know his work, you know “regular” is far from what the case will turn out to be). Small town detective Ralph Anderson (played in the HBO series by Ben Mendelsohn) arrests a little league coach for the brutal rape and and murder of a neighborhood kid. The coach, Terry Maitland (played by Jason Bateman, who also directs the first two episodes and serves as executive producer on the series), insists he is innocent and provides witnesses and video to back him up. But the cops also have witnesses and video that say he is guilty. Enter Holly Gibney (played by Cynthia Erivo) to do a bit more digging and, eventually, find an otherworldly answer for how it could appear that Terry was in two places at once.

Price notes that when he first sat down with the material he was hoping he could cover the whole book in one season. When he actually began translating the rich prose to screenplay format, he found he was speeding through it faster than he ever expected. “By the time I was writing the third episode I was more than halfway through the book, and I had seven hours to go,” he shares. “The book was so gripping and moved so fast. I just felt like to slow that down would be doing a disservice to the tempo, to the tension. You knock people out for two hours and then you take a breath.”

Price says that he didn’t approach this adaptation assuming the audience already knows the book: “You have to kind of write it like there was no book because if you write it with any kind of assumption, you lose them right away,” he says.

To that end, he had no qualms about “adding and reinventing and creating people that weren’t in the book” to further flesh out the story.

“It’s definitely his story, for sure, and his characters,” Price says of King, “but adding this wrinkle or this location, and the whole point of that is to keep it as fascinating as you can. The only thing a script of any kind owes to a novel that’s being adapted is the spirit. You have to make compromises for the medium. A book is four-dimensional because the book can give you the inner thoughts of a character and the book also has actual writing in it, where screenplays just have dialogue and Post-it notes for the director. I had to translate a lot of stuff that a novelist would have the freedom to say in exposition.”

One key change was in Ralph’s struggles as he has to dig deeper into an investigation for a case he thought was open and shut.

As a detective, “he believes only in things like witnesses’ statements, interviews, DNA,” Price says. “His goal is finding hard stuff that will lead to a conviction. He’s not going to worry about child psychology; he’s not going to worry about philosophy. He’s, ‘Where are the prints? I think that witness was lying, bring him back.'”

All of that was true in the novel, and it is in the show, as well. But, in the series, Ralph has lost his son to cancer, which adds an extra emotional layer to how he reacts in certain situations and also plays into the larger theme of grief that becomes an important part of the story when more is known about who killed the young boy.

“I needed Ralph to have more of a personal stake in the loss of children,” Price says. “I think in the book Stephen told me that he wanted to get the kid out of the picture so he sent him to a summer camp, but I was under the gun to make Ralph deeper, and that’s the invention I came up with. And as you write more, it presents things to you like, ‘Oh yeah, if Ralph has lost a kid, in this situation he would feel this.’ It just develops.”

Price also tweaked the character of Holly a bit. A modern King classic, Holly first appeared in his 2014 novel “Mr. Mercedes” and is actually a character on AT&T Audience Network’s adaptation of that novel, as well. Price says he has only seen “maybe 20 minutes” of “Mr. Mercedes” and admits he didn’t want to know much about her in that show or in the book on which it is based. After all that, version of the character is 15 years old and already different from who she is in his source material. But furthermore, “I don’t want to be beholden to something,” he says. “Holly was like that then, but this is my adaptation, and my job is to make Holly as compelling as possible. I have to do what I have to do, and I’m not beholden to fans or loyalists. I just want to do the best job and make the most complex and three-dimensional character that I can.”

Holly doesn’t enter “The Outsider” until the third episode, in part because she doesn’t enter the novel until Ralph is already deep in the investigation and new perspective is needed. Price followed the same timeline and tentpole moments in his version of the story, and his version of Holly also has to represent that unique perspective.

“She can talk about all of the foreign names for the boogeyman and then talk about what song was No. 7 on Jan. 3, 1958 on Billboard’s Top 100 rock and roll and how’d it do the following week? She’s just one of these people who, if they become focused on something, they become computers. She could also tell you how tall a building is after looking at it for two seconds. The whole point of Holly is when she says, ‘If you have no tolerance for the unexplainable then you’ll have no tolerance for me.’ She is an enigma to herself and all of the people around her since childhood,” he says.

She is also more openminded than Ralph when it comes to the supernatural and is the one who finds ties to those elements in this case. This means those elements are not floated as a possibility until later in the season, as well.

“It’s tricky, but I had a really good story to work with, so I just wanted to keep the characters and the sequence of events,” he says of introducing the supernatural after the audience has gotten used to a straight detective story for a few episodes.

Price found his way to “make Stephen King’s characters’ rich interior life into physical life” for the on-screen version of “The Outsider,” and it is King approved. Last month he Tweeted that Price’s version blew his mind and is “the perfect winter’s tale.” Price, who acknowledges he did want to do a good job with this one, partially because he’s had a mutually admirable relationship with King over the years, calls that stamp of approval “very flattering and very gratifying.”

And he does see ways in which certain characters and the world can continue beyond this one 10-episode season. Similar to how David E. Kelley adapted Liane Moriarty’s “Big Little Lies” novel for one season and then took a new original story from Moriarty for the second season, Price says if he should do more of this show, he would want it to come from source material again.

“What’s hardest for me is writing an original 10-hour story because my impulse, if I have a really great idea for a big story, I’m going to write a novel. What I love is when I have really good material that someone else figured out for the novel,” he explains. “It’s better for me not to have a personal relationship with the material. When I’m adapting my own stuff, it’s like I’m a doctor and my appendix burst and I guess I’ll just take it out myself, but really you should get another doctor.”

“The Outsider” premieres Jan. 12 on HBO.