King James is set to release "I Promise" on August 11 -- a 40-page picture book featuring "upbeat, rhyming text," based on a poem written by LeBron.

The artwork was all done by famed illustrator Nina Mata -- who also worked with Team USA Olympic gymnast Laurie Hernandez on her kids book, "She's Got This."

Bron says the title is in inspired by his "I Promise" program -- which "motivates children everywhere to always #StriveForGreatness."

Of course, Bron opened his "I Promise" school for at-risk children in Akron back in 2018 ... where students made huge gains in statewide testing after the first year!

LBJ's book is super positive -- with simple, inspiring messages like:

"I promise to use my voice and stand up for what's right."

"I promise to ask for help whenever I need it."

"I promise to be me."

Oh, and Bron is also dropping a companion audiobook read by his mom, Gloria James!

Bron spoke about the project ... saying, "Books have the ability to teach, inspire, and bring people together. That's why these books, and the opportunity to get children and parents reading together, mean so much to me."

But, this isn't a one-and-done project for the King ... James is also working on a "middle grade" book which is due in 2021.