Interest levels reflect the difficulty level of books in terms of the issues they present. Interest levels are a good indication of whether a book includes adult situations or strong language. They do not indicate how difficult the book is to read; in fact, many books with an upper grade (UG) interest level (books that handle mature issues) are written at elementary and middle-school reading levels so that they are easier to understand.
In AR BookGuide, there are three interest levels: lower grades (LG), middle grades (MG), and upper grades (UG).