You can try. Normally Steam don't give refunds, I tried myself when I bought Aliens: Colonial Marines and the game was NOTHING like the demo, it was a shitfest.
"As with most software products, unless required by local law, we do not offer refunds or exchanges on games, DLC or in-game items purchased on our website or through the Steam Client. Please review Section 3 of the Steam Subscriber Agreement for more information."
"An exception is made for games purchased during a pre-order period if the request is received prior to the games' release date."
The release date is 7th November, but the beta has already been released and you've played it. So it depends what Steam consider to be release date - beta or full release.
EDIT: I think you'll struggle to get a refund, considering they are very clear on the following points, even writing it in caps lock in their subscriber agreement:
"YOU DO NOT HAVE A RIGHT TO WITHDRAW FROM A TRANSACTION OR OBTAIN A REFUND ONCE DELIVERY OF THE CONTENT HAS STARTED OR THE PERFORMANCE OF THE SERVICE HAS COMMENCED, AT WHICH POINT YOUR TRANSACTION IS FINAL. YOU AGREE THAT DELIVERY OF DIGITAL CONTENT, AND THE ASSOCIATED SUBSCRIPTION, AND/OR PERFORMANCE OF THE ASSOCIATED SERVICE, COMMENCES AT THE MOMENT THE DIGITAL CONTENT IS ADDED TO YOUR ACCOUNT OR INVENTORY OR OTHERWISE MADE ACCESSIBLE TO YOU FOR DOWNLOAD OR USE."