In her video, Hoover was very excited as she made the announcement.
"Blake Lively y'all, she's my dream Lily. Then when I first met Justin Baldoni who's directing the film (...) I immediately wanted him to be Ryle," she said.
"I think that Justin Baldoni and Blake Lively have what it takes to bring these characters to life."
Following Thursday's announcement, Lively posted an Instagram story showing off her new brunette look as she possibly gets ready to take on her new role.
Blake Lively in an Instagram story on Jan. 26, 2023.blakelively | Instagram
It Ends With Us follows a small-town girl Lily who moves to Boston to start her own business. She then meets and falls for neurosurgeon Ryle Kincaid.
"As questions about her new relationship overwhelm her, so do thoughts of Atlas Corrigan — her first love and a link to the past she left behind. He was her kindred spirit, her protector," the book's description reads. "When Atlas suddenly reappears, everything Lily has built with Ryle is threatened.”
Fans are now waiting to see who will be cast as Atlas.
As for reaction about Lively and Baldoni's casting in the film, that reaction has been mixed online.
One Twitter user was disappointed by the casting announcement and included photos of the actors they think would have been a better choice for the roles.
"I think they picked Blake Lively because of her reputation and not keeping the character lily in mind."
Another person posted a GIF of themselves "going back in time to stop blake lively from auditioning" for the film.
Another person also stated the casting decision for Blake Lively "was not on my 2023 bingo card at all."
Reaction was much more positive in the comments section of Hoover's Instagram video with many people saying the casting choices are "perfect."
"SCREAMING! CRYING! This is perfect," one comment reads while another person wrote, "COLLEEN I AM CRYING FOR YOU!! Blake fricken Lively!!!!!! LETS GO!"
According to Variety, Hoover is currently the highest-selling novelist in the U.S., and wrote five of the top 10 bestselling books of any genre in 2022.
It Ends With Us was first released in 2016, but really blew up on TikTok last year. Variety reports it was on the New York Times' bestseller list for over 90 weeks.
Hoover has previously explained how the inspiration behind It Ends With Us is loosely based on her mother.
In her Instagram video Hoover stood in front of her old house where her mother brought her and her siblings after leaving their abusive father.
"Thank you, Mom, for making that very difficult decision. This house holds nothing but wonderful memories for me," Hoover said.
Christy Hall will be adapting the script for the film, which is in development with Wayfarer Studios and Sony Pictures.
The release date is unknown at this point.
