Study guides or study notes go beyond book summaries. Intended mostly for students, guides aim to add value by providing analysis and study aids. Study guides could be a 75-page PDF — or longer. Options include Spark Notes, Cliffs Notes, BookRags, A-Plus Notes. Study guides like Cliff Notes tend toward classic literature such as Macbeth or educational topics like biochemistry, not the latest business books. The better ones like Spark Notes or Cliffs Notes offer a mobile app, too. Teachers may also find them valuable.