The work is called "Dear Black Boy" ... and Bennett told TMZ Sports this week it's a tale aimed at encouraging young Black boys to follow their dreams in any field -- not simply the sports world.

"When I look at Black boys, I don't see athletes," the former New England Patriots tight end said. "I see a world of possibilities within them. So, I ask them, what are they interested in, not what they play."

The book is several pages long ... and one of the main mantras throughout it is "run towards freedom."

Bennett said that line is meant to tell youngsters to pursue "the freedom of self-expression to become anything that you want to be in life."

The piece is actually not Bennett's first foray into children's books -- he's written multiple in the last decade ... as he said his life after football has been filled with art.

In fact, Bennett -- who played in 144 games in his 10-year NFL career -- told us he doesn't really even watch football these days ... as he spends most of his time being creative.

"There's never been a day in my life since I retired I didn't make something," he said.