In the real world, even the most ideal forms of love come with their own complexities and struggles. A relationship between two people who are meant for one another should never be outright difficult, but there must be a common respect, a give-and-take, a sensitivity of each other's thoughts and emotions. This is what 27-year-old Calvin Weir-Fields (Paul Dano) is missing. An author who made headlines in high school when he published his best-selling first novel, he has since struggled with a severe case of writer's block. As the world waits for his next book—he has only released some short stories and a novella in the intervening ten years—Calvin has been overwhelmed by the pressure to live up to, and surpass, his debut. He's too self-involved for a girlfriend until he experiences a dream that he promptly writes down. The fictional female character he comes up with, Ruby Sparks (Zoe Kazan), is very nearly the perfect girl for him, an unspoken notion cemented when she suddenly shows up in his house, a living, flesh-and-blood creation.

Directed by Jonathan Dayton and Valerie Faris (2006's "Little Miss Sunshine"), "Ruby Sparks" is a tender, if rightfully uncomfortable, love story. Nostalgic and whimsical, but with a necessary dark side, the film is the brain child of actress Zoe Kazan, who penned the screenplay and plays the title character. The very idea of writing a human being into fruition is a far cry from plausibility, but it's terrific cinematic fodder, particularly since Calvin—and the only other person he lets in on his secret, elder brother Harry (Chris Messina)—react just as anyone would if faced with such a situation: in disbelief, wonder, and maybe even a trace of fright. Initially molded precisely into the person Calvin has described in his story, Ruby is at first the embodiment of Calvin's soul mate. They get along so well that he stops elaborating on who she is and what she's going through. From this, Ruby blossoms into her own self, a young woman who begins to naturally question why she's stuck in the house doing nothing and starts to develop her own aspirations and yearn for friends. Not just at Calvin's whim anymore, Ruby faces a diverse scale of emotions and the feeling that she should have more independence. In return, Calvin starts to see her slowly slip away from him. He can change what's on the page, yes, but does he have the right to any longer? Is the problem Ruby, or might it be his own selfishness that has driven her away?

"Ruby Sparks" deals in a scenario that is not, by the basic laws of reason and physics, possible, but everything else about the film is nothing short of believable. There is the spark, for lack of a better word, of exploitation and misogyny in the way Calvin silently yields his power over Ruby, turning her French one moment and solving all her woes by writing down that she's as joyful as she's ever been (that one's a big mistake). And yet, Calvin is not cruel so much as desperate to hold on to a relationship that was special for a time, but might have ultimately run its course. For it to work again, he would have to do some growing up and learn a few things about compassion and selflessness. Perhaps this is what's missing from his recent writing. Maybe, through the very act of knowing Ruby, he has the chance to finally reclaim what he's lost.

It is always chancy to cast an actual couple as onscreen paramours, but Paul Dano (2011's "Cowboys & Aliens") and Zoe Kazan (2009's "It's Complicated") are a match made in the same indie-romance heaven that Joseph Gordon-Levitt and Zooey Deschanel derived from for 2009's "(500) Days of Summer." Dano plays Calvin as slightly awkward, a little shy, and unabashedly likable. The luminous Kazan plays Zoe as a ray of light who deepens the longer she exists in the world. She helps him out of his shell. Now he needs to help her find her own path. Annette Bening (2010's "The Kids Are All Right") and Antonio Banderas (2012's "Haywire") show up for a brief interlude where Calvin brings Ruby to meet his mom and her significant other. He makes mention of how much she has changed since meeting this earthy guy who carves furniture out of wood he finds, but the subplot is dropped immediately after. One has to wonder if actors of Banderas' and especially Bening's stature were in the script more than they've ended up in the final cut. As is, these tiny roles are beneath them.

Something of a grown-up fairy tale that plays it straight, "Ruby Sparks" humanizes its mystical title character—a 26-year-old gal who has no idea she's the product of someone else's imagination. As a writer, Zoe Kazan finds insight in the life of an established writer in stasis while also gracefully building a love story that is bittersweet but somehow true, despite its dips in fantasy. How she works out the premise's biggest leap from reality without needing to overexplain is just right. As an actress, Kazan makes Ruby as real as anyone. By the end, she has long earned the right to live her life, no matter how she came to be. Aren't all of our existences something of a cosmic mystery, anyway? "Ruby Sparks" is delicate, unassuming, and, like Ruby herself, kind of difficult not to fall for.