Reading Levels for Children's Books

Babies to Beginning Readers - teaches basic concepts and uses a limited, beginning vocabulary.  Text is in a very large typeface and usually consists of single words and phrases or can be very simple sentences or rhymes designed to be read to the child.  Always illustrated.  Usually less fewer 24 pages.
Beginning Readers to Early Readers - Almost always illustrated and usually uses a larger type face (14-16 pt), a basic vocabulary and has fewer than a paragraph on each page.   Usually does not have chapters and has less than 50 pages.
Early Readers - Most are divided into chapters (chapter books), but not all.  Often a large type face (14 pt) but not always.  Usually has a varied but uncomplicated vocabulary, simple plot development and non-controversial themes.  Typically has lots of illustrations, but with at least a paragraph on each text page.  Typically from 30 to 180 pages or more.
Middle Readers - Usually has an easy-to-read type face (12 -14 pt), titled chapters, and at least a few illustrations (often on the chapter title pages).  Uses a broad vocabulary and maturing themes often with plot twists and surprise endings.  Typically has between 150 to 250 pages, but can be more or less.
Young Adult - Similar format as regular adult novels: regular type face (12 pt), few or no illustrations, mature vocabulary.  Often has complex plot development and well developed characters.  Can have controversial content and themes.  Typically has fewer pages than adult books, usually 200 to 300 pages, but can be more or less.