In The Last Letter From Your Lover, best-selling author Jojo Moyes (Me Before You) depicts two women's lives across two different decades in the 1960s and the present. The film adaptation of her novel arrives on Netflix on July 23, bringing both time periods to life for the summer.

Socialite Jennifer Stirling (Shailene Woodley, The Mauritanian) falls deeply in love with Anthony O'Hare (Callum Turner, Emma), but she's unhappily married and therefore constrained from pursuing him. In the present, journalist Ellie Haworth (Felicity Jones, On the Basis of Sex) discovers a love letter from him in the middle of researching another story. As Ellie investigates their romance, she also entertains her own new connection with Rory (Nabhaan Rizwan, 1917).

Related: Shailene Woodley & Callum Turner Interview: The Last Letter From Your Lover

Moyes spoke to Screen Rant about the process of adapting the novel for the screen and how she feels about the casting.

Last Letter From Your Lover - Ellie Haworth & Nabhaan Rizwan

Screen Rant: What was the collaboration process like for you? How did you contribute in the pre-production stages with the writers and director?

Jojo Moyes: This has been very long in the pre-production stages. I don't know if you know, but this was originally optioned 10 or 11 years ago. It's been a really long labor of love to get this to screen.

I've always kept in touch with the producers but, when they originally optioned it, I wasn't writing scripts. There was no question of me adapting the work - plus, I wasn't sure I could do it because it has a complicated time structure. Esta Spalding was the first writer who came aboard and then Nick Payne. And it's been great because, by the time they got a script into shape that was ready to shoot, I was much more experienced in the filmmaking process and I was able to contribute notes. From the moment I met Augustine Frizzell, the director, I liked her enormously and was able to talk to her. I've been sitting in editing; I came on set.

So, although I didn't write the actual scripts for this one, I've been very much a part of the process. And for me as a writer, that's a real privilege and something that you have to be careful of. I think, as a writer, you can't just steam in and demand everything is done your way. You have to respect a director's vision. Luckily, I think Augustine's vision is a great one.

I love just how connected Jennifer and Ellie feel, even though they don't know each other at all. Can you talk about how much you felt Shailene and Felicity embodied the vision you had for those characters?

Jojo Moyes: Jennifer, originally in my book, was a blonde. I had to make a little mental leap, but I was such an admirer of Shailene's work that I was happy just to see what happened. And then she was just so good, and so heartbreaking, and so embodied the spirit of my Jennifer that I kind of forgot about hair color completely. I think she makes you feel every emotion that Jennifer feels when she's on screen. You are totally with her; you're yearning, you're sad, you're happy, you're giddy. She's just extraordinary.

As for Felicity, I've always been a huge admirer. We kind of wanted to work on a different project together a long time ago, so when I heard that she was attached to this, I was really excited. For me, it was a huge surprise that she wanted to be Ellie, because Felicity traditionally has played quite formal characters, I'd say - quite well behaved, maybe a bit buttoned up. And I think the thing that people are going to be surprised by is how funny she is.

Ellie is a messy character. She says and does the wrong thing. She's a little bit out of control at the start of the movie and I just love seeing Felicity run with it. There's an eating scene in it, which just makes me die laughing every time I watch it. She's got comedy chops.

You have plenty of wonderful novels that could be adapted into films and now you've even worked on the script for Me Before You. Is there any other story of yours that you'd like to see adapted or that you'd like to adapt yourself?

Jojo Moyes: I have a funny attachment to a little book that I wrote called Silver Bay, way back when. It didn't do huge business when it first came out, but it was such an emotional book for me and it's quite a tight little story. I would love to see that one, make it onto screen.

But I will say that a lot of it takes place on boats. One thing I now understand about the film business is anything you put a water costs about twice as much to make. I don't know if that will ever happen, but I'm happy with anything of mine.

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The Last Letter From Your Lover drops July 23 on Netflix.