Ruby Sparks suffers from its marketing. This is because it's a high concept film (which is that an author wakes up one day and finds that the character he's writing is living in his house) that takes two reels to make that point, over half an hour to get to that she's real and not just a figment of his imagination, and then spends another half an hour labouring through the beginnings of a relationship that the trailer short-handed in under a minute. You could watch the trailer, then the last 45 minutes of this film and probably get more out of it.
Being a film so reliant on its central concept to provide the bulk of the interest (that the writer can change her behaviour by writing something else about her), it deals with this in such obvious and contradictory ways it's clear that writer/producer/star Zoe Kazan got her writing skills from her hack of a mother (Robin Swicord, who decimated Memoirs of a Geisha and picked up an oscar nomination for ...Benjamin Button for having done a previous draft) rather than her legendary grandfather (Elia Kazan), and doesn't have a whiff of a coherent point.
This is because Kazan very clearly sets up that Paul Dano's character (the writer) doesn't know anything about women, having his brother (a rather fun Chris Messina) inform him of that and point out that the character he's written is fundamentally unbelievable and an unreal non-person. What the film ends up saying though is that Dano should have left her the way she was rather than submitted to the temptation to change her personality to suit him better. It never makes the point that he'd created an impossible ideal, or someone who couldn't exist (as the set up implies), but instead becomes a ham-fisted metaphor warning against the ills of trying to change the person you're with.
Legendary music video directors Jonathan Dayton and Valerie Faris (of Little Miss Sunshine fame) do what they can to infuse the script with a youthful verve by utilising some appealing visuals and a fitting soundtrack, but in sticking to the plodding structure it becomes an exercise in trying to make the most of every linking montage or set piece possible. The acting is fine in the main, aside from a lifeless central turn from Dano which drags everything down and kills any emotional investment in a character that has nothing interesting about him as a person on show. The saddest thing about this is that it becomes such a chore to get through, when the trailer at the very least suggested it would be anything but. It would still have a myriad of problems anyway, but the way they sold the film amplifies them even more.