The story should sound good when read aloud. It should sound good to the listeners and feel good to the reader. Are all the words in the right place? Does the author use precise language? Does the language flow smoothly?
A rhyming book should read in a natural and comfortable way. Is it rhythmical? Does the rhyme seem forced? Are the words well chosen or just used to fulfill a rhyme scheme?
The illustrations should be engaging, interesting and designed for children. When you look at a book, consider whether your children will respond to the illustrations.
The illustrations should be a perfect match for the text. Whether bright or soft, realistic or cartoon, they should complement the story.
The illustrations should expose children to a variety of artistic styles - watercolor, oil paint, collage, cartoon, photography, block prints, and more.
Children's books should be free from gender, ethnic, racial, and religious stereotypes. Is the book dated in its depiction of any individuals or groups? Is the experience shown authentic, that is, is it based on the author's deep knowledge and/or experience of the culture?
Children should have access to some books that reflect their own lives and experiences, as well as to books depicting the diversity of the larger society.
Taken from The Fred Rogers Company website: http://www.fci.org/best-books-babies/index.html