Blake Lively 'Exceeded All My Expectations' in “It Ends with Us”, Raves Author Colleen Hoover (Exclusive)

Director and costar Justin Baldoni adds, "I believe it's Blake Lively as you've never seen her before"

Colleen Hoover has enthusiastic praise for Blake Lively's complex performance in It Ends with Us.

The upcoming romantic drama marks the first big-screen adaptation of one of Hoover's blockbuster books. The author tells PEOPLE the process has been "absolutely incredible and surreal."

"Everyone involved has been so dedicated about making this adaptation as faithful and heartfelt as possible," says Hoover, who is also an executive producer on the film. "It's been a true team effort, and I can't wait for those who loved the book to see the movie and experience the magic they’ve created on the big screen."

A key piece of that magic is Lively as Lily Bloom, a woman starting up her own business in Boston who sparks a volatile relationship with a charismatic neurosurgeon named Ryle Kincaid.

Related: Blake Lively and Justin Baldoni Share Emotional First Look at It Ends with Us (Exclusive)

Hoover says Lively, 36, gives a "captivating, stunning and emotional" performance.

"There aren't enough words to describe her phenomenal talent," says Hoover. "Blake Lively truly brought Lily Bloom to life in a way that exceeded all my expectations."

"When I wrote Lily’s character, I thought I had a fairly solid image in mind," she adds, "but Blake's portrayal added so much depth and complexity to the character that I didn't even anticipate."

Hoover explains that the "most impressive" part of the actress is "her ability to convey her character's internal conflicts and external challenges with such nuance and subtlety."

"I am in awe, truly," says the author. "I couldn't be more grateful for her incredible performance."

Related: ‘It Ends with Us’ Cast: Here’s Who’s Playing Lily, Ryle and Atlas in the Movie Adaptation

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Justin Baldoni stars opposite Lively as Ryle and also serves as director of It Ends with Us. He hails Lively's take on Lily as "strong, funny and intelligent — all the things you want from female heroine."

"I think people are going to be blown away by her portrayal of Lily," Baldoni, 40, tells PEOPLE. "It's so nuanced, it's so unique, it's so beautiful. I don't want to give away too much, but I believe it's Blake Lively as you've never seen her before."

Baldoni adds that there "wasn't a part of this production that [Lively] didn't touch and have influence on." And, he says, "everything that she put her hands on and her mind to, she made better."

Related: Colleen Hoover’s 26 Books, In Chronological Order

Now eight years since It Ends with Us was first published, Hoover says she "definitely felt so much while watching the adaptation."

"The movie experience adds another layer to the connection readers already have with the characters," she says. "The power of visual storytelling is undeniable, and it can evoke even stronger emotions and empathy from the audience by bringing a sense of immediacy and intensity to the story."

Lively says she hopes her love for the character and the material shines through.

“Lily resonated with an enormous amount of people, as the success of the book made clear," says the star. "Stepping into a character who’s had such a meaningful impact is an honor to take on. I loved Lily, and I hope that love is felt by those who care about her like I do, and also those who are getting to know her for the first time in this film."

It Ends with Us is in theaters Aug. 9.

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