After a small critique it was suggested that perhaps the style of design was too basic: details on the hands for example or the shape of the girl in the centre. A more intricate approach could have perhaps looked more professional. This is a valid consideration, however since the design is for children it needs to be viewable and easily understood by a younger audience. So by using minimal line and rounded shapes it can appear more friendly, balanced with the dark colours of the cover.
Another suggestions was that perhaps the design shouldn't have used black and white so heavily within the design, as this is something that a lot of the entrants might use. However with the accents of purple I think this balances out the appearance. It's also important to convey the nature of the book with the content being very black/white and night/day in nature. Some positive feedback was that the design flows quite well, with the eyes following down the direction of the arms to slowly intake the whole design.