I have read what you have posted up so far on your book and here is what I think (I'm not lying this is my actual opinion of your story):
Interest: It started of okay in terms of interest, but as your book went further it got more interesting and had more of an effect that said 'I have to read more.'
Grammar: There were a few spelling errors and there was a time that you repeated a few words. There was also another when you forgot to use spaces but apart from that your grammar was very good.
Plot line: Your plot line seems very interesting.
Overall: It was very good and I think that if I can I might come back when you have written more and read your new bits in the story.
Rating out of ten: 9