I would suggest books that offer a variety of points of view. By this I'm not referring to first person, third person or omniscient. I'm talking about books the focus on kids in different life situations. Boys, girls, Hispanic, smart, poor, etc.
In my view
1. Should be very interesting, capture and hold the kids' attention storywise
2. Should have visual and oral impact, kids should be attracted to it
3. Should reflect variety i.e. a variety of stories, over a wide area, no 'sameness'.
4. Should make the kids think, or ask questions, or 'awaken' them in some way
5. Should also give a limited amount of knowledge--of new vocabulary, ideas, information, other types of knowledge
hope this helps.