A.J. Brown Explains Sideline Reading During Wild Card Win, It Gives Me Peace!

11:38 AM PT -- TMZ Sports caught up with author Jim Murphy on A.J. Brown's viral moment ... and he said he's grateful the receiver is bringing attention to the contents of his book.

Murphy said he was aware Brown got his hands on his work ... but had no idea he was holding onto it so much that he had it on him during games.

As for whether he'd like to meet up with Brown, Murphy said he doesn't want to be a distraction amid the team's playoff run ... but provided some knowledge on what they can focus on to succeed even more.

Philadelphia Eagles star A.J. Brown went viral for cracking open a book right on the bench during his team's Wild Card matchup with the Packers on Sunday ... but he says it's actually nothing new -- 'cause reading gives him a sense of peace mid-game.

Clips of Brown's impromptu book club session quickly made rounds on social media ... with some folks assuming having his nose deep in "Inner Excellence" by Jim Murphy was a sign of rebellion amid his quiet day on the field.

Brown cleared the air with reporters in the locker room after the 22-10 victory ... and he said he always has the literature by his side on gameday -- it's just the first time it's been caught on video.

"Man, it gives me a sense of peace," Brown said. "That’s a book that I bring every single game. My teammates call it the recipe. That’s the first time I heard that y'all got me on camera. But, it’s not the first game."

Brown explained his book choice, which was a recommendation from teammate Moro Ojomo, saying it's filled with a lot of knowledge that helps him on the mental side of football.

"I physically believe I can do anything and everything but I gotta make sure my mental good."

Brown's an avid reader ... and he's known to try to knock out two every month. But, as shown in the snap of his copy of Murphy's work, it's clear he loves to revisit it ... and it even has highlighted paragraphs and sentences.

"I go back to it," Brown said. "It also says if you’re humble, you can't be embarrassed. So no matter what happens in a game or no matter what happens, I'm just going to stay free and play free, keep going, take risks."

Brown had one catch for 10 yards in the matchup ... but if he keeps reading up on that book, he'll be ready when his number's called next week.

As for the author, he's well aware of Brown's reading material ... giving the NFLer a shoutout on social media.

It's also worked wonders for his sales ... as it's one of the top sellers on Amazon at the moment.