hmm....kowsar going very good....few comments -
Book 1: red one doesn't go as a overall color. pick some colors from the front artwork. book 2/3 are the perfect example. they are nice. try some different shades for book 1.
didn't like the back.
suggestions- before design books, go through some international books/children books from net or nearby book store. this is the only option to do good design. what you will look in those books? - how they aligned texts, what font sizes they used for heading and body texts, line spacing, what fonts, how close the letters are from each other like this. your design will be better day by day if you study those since you are doing some books for children.
keep it up.
