I have to say, I'm a little miffed that Waterstone's are promoting this as an opportunity to 'have lunch with the authors of Stormslayer'*. It would have been better if they'd said have lunch with the creators of Fighting Fantasy, as it's all about the brand now anyway.
But, other than that, its a cool competition, so why not enter yourself? After all, what have you got to lose?
*You could have them under the trade descriptions act for that.