Definition: picture book
A picture book is a book in which the illustrations are as important as (or even more important than) the words in telling the story. Picture books are generally 32 pages long, although Little Golden Books are 24 pages. In picture books, there are illustrations on every page or on one of every pair of facing pages. While most picture books are written for younger children, in recent years, a number of excellent picture books for upper elementary and middle school readers have been published. The terms "picture book biography" and "picture book history" refer to nonfiction books written and illustrated in picture book format.
The definition of "picture book" was greatly expanded when Brian Selznick won the 2008 Caldecott Medal for picture book illustrations for his book The Invention of Hugo Cabret, a 525-page middle grade novel that told the story in a series of sequential illustrations (more than 280 pages interspersed throughout the book) along with Selznick's words.