How to follow up a classic - that's one of the big questions at the heart of Ruby Sparks. The movie's main character, played by Paul Dano, is a high school dropout who found himself at the top of the New York Times bestseller list at 19. The movie's directors, Jonathan Dayton and Valerie Faris, are the duo who cast Dano in their glorious, timeless study of family dysfunction and what it means to love, Little Miss Sunshine.

Calvin Weir-Fields (Dano) is a lonely introvert who lives in a soulless-but-swish apartment and is broken from carrying around the weight of his past success. It's been 10 years since his masterpiece; he really has no-one outside of family to share his life with (and even then...) and contends that girls only want to sleep with him because they read his book in high school. Calvin's days revolve around gym sessions with his well-meaning and well-adjusted brother Harry (Messina), sessions with his psychiatrist (Gould), walking the dog and attending readings of the book he wrote as a teenager, where people call him a genius and ask him when his next one is coming out. By the looks of things, it isn't.

But then something, or rather someone, shakes Calvin out of his torpor. Ruby Sparks is an aspiring artist who "can't drive, doesn't own a computer and always roots for the underdog". She's the girl of Calvin's dreams - literally. After imagining her as part of an exercise for his psychiatrist, Ruby has come to life: a real person who other people can see but whose thoughts and actions are controlled by Calvin through the keys of his typewriter. The creative juices (in art and elsewhere) start flowing again and Calvin becomes a man reborn. But just how will such awesome power be used by someone who was so self-obsessed to begin with?

Written by star Kazan (a rookie screenwriter, no less), this small, offbeat study of a man and a woman offers good insights into the messiness of relationships, our inability to live in the present and the tendency to try to mould our significant others into ourselves. As date movies go, it's a good one for getting the conversation going afterwards, but given the premise and Dayton and Faris' previous form it should have delivered a lot more belly laughs. Ruby Sparks fails to make the most of the talent at its disposal - Bening and Banderas only really feature in one weekend away sequence and Gould gets just the one big scene - and the potential for more keystroke-driven mischief isn't fully realised - Coogan's fans may feel particularly short-changed.

If you've seen To Rome with Love and are still suffering badly with the Woody withdrawals, by all means go - it's no chore to watch. But there are better movies out there. Or you could, of course, just stay at home and read at book...

Harry Guerin