ProjectMuse has full-text scholarly articles from many journals in the humanities.
JSTOR has full-text scholarly articles from journals in many disciplines.
If you are working with a book published recently, you will probably not be able to find peer-reviewed or scholarly articles about it; the publication cycle in the humanities takes many months or possibly even years.
If you have difficulty finding an article about your book, look for articles about the theme or focus in question as it relates to other works of fiction. For example, if you are researching The Hunger Games, you could look for articles about violence or dystopian or apocalyptic futures in other books. Consider how these readings or interpretations help to illuminate The Hunger Games.