This is going to be a really hard month to vote on, seriously...

I know none of the characters of anyone's stories. Jokes and references will be lost on me. And there is hardly any room to develop character, or their specifics, and build the story at the same time.
Even as I work on mine I realise it's going to be extremely hard to enjoy and grasp for anyone who hasn't read the book of my MC, because of the somewhat complex magic he uses. I've had to cut down references because they'd be opaque.