George Karl blasted Carmelo Anthony in his new book, ripping the Knicks star’s attitude, leadership ability and addiction to the spotlight.

Karl, Anthony’s coach for six years with the Nuggets, called him a “true conundrum” and “a user of people.” Karl also criticized Anthony’s unwillingness to play defense and said being a scorer doesn’t “make him a winner.”

“Carmelo was a true conundrum for me in the six years I had him,” Karl wrote in his memoir, “Furious George,” which is due out in January. “He was the best offensive player I ever coached. He was also a user of people, addicted to the spotlight and very unhappy when he had to share it.

“He really lit my fuse with his low demand for himself on defense. He had no commitment to the hard, dirty work of stopping the other guy. My ideal — probably every coach’s ideal — is when your best player also is your leader. But since Carmelo only played hard on one side of the ball, he made it plain and simple he couldn’t lead the Nuggets, even though he said he wanted to. Coaching him meant working around his defense and compensating for his attitude.”

Anthony originally said he didn’t have any comment because “it’s irrelevant” and joked that he will address it when he writes his book. He mostly took the high road, saying he hopes Karl “finds happiness,” but said he was surprised.

“It’s tough,” he said. “If this would have came out years ago — I haven’t been in Denver in six, seven years, I haven’t played under him in six, seven years. When you’re there, it’s a different story than what you hear after the fact.

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“I never knew it was this much. I never knew I was a — what was the word — conundrum? I don’t even know what the hell that means, to be honest with you. I never knew that. That never was brought up. Anybody that you ask, assistant coaches, players, front-office people, anybody you ask will sing a different tune when it comes to me, when it comes to our mentality, that team.’’

Knicks coach Jeff Hornacek defended Anthony. “The biggest thing is Carmelo for us has been great,” he said. “He’s done everything we’ve asked and what the coaches want him to do. He’s been a great leader for our team . . . He’s been a great player for a lot of years.”

Karl also took shots at former Knicks and Nuggets players J.R. Smith and Kenyon Martin.

He said Smith had a “huge sense of entitlement, a distracting posse, his eye always on his next contract and some really unbelievable shot selection.”

Knicks president Phil Jackson drew the ire of LeBron James and hip-hop mogul Jay Z, among others, for referring to James’ friends and business partners as a “posse” in an interview last month.

Karl called Martin “insecure, immature,” in part because he had no father growing up. Martin responded with a series of tweets, calling Karl “a terrible person” and “everyone that’s played for that awful person and coach can’t stand the ground he walks on.”

Anthony has evolved as a player and has been a more willing passer with the Knicks. But Karl said he didn’t think Anthony “cared enough about being a good teammate.”

Karl also said “getting rid of Carmelo Anthony was a sweet release for the coach and the team, like popping a blister,” and that the Nuggets “won the trade, definitely.”

“He and I had a little conflict bubbling,” Karl wrote about Anthony’s trade demand. “I want as much effort on defense — maybe more — as on offense. That was never going to happen with Melo, whose amazing ability to score with the ball made him a star but didn’t make him a winner. Which I pointed out to him. Which he didn’t like.”

After Anthony was traded, Karl said the “ball rarely stopped for an isolation play.”

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Jackson said something similar two weeks ago about Anthony, who fired back at Jackson on Instagram and Twitter.

Anthony said he wasn’t disappointed by what Karl wrote.

“Nothing disappoints me anymore,” he said. “I’m past being disappointed. I just hope that he finds happiness in what he’s doing. His book hopefully will bring him happiness.’’