Does Size Matter?

So, without going into a ton of detail, my newest book is a fairytale.  Well, a complete rewrite of an already well-known fairytale.

Compared with Carving The Light, this one is a lot lighter and more fun to write.

But are there fairytale-writing rules that I should know about?  For example, does the length of it really matter?
I have the entire story pretty much worked out in my head already.  It's actually so complete in there that I am almost annoyed at having to actually write it all down.  ...