Unique Learning System Leveled Books are evaluated using a set of guidelines that examine text characteristics and the demands placed on the reader. Once evaluated, each book is then given an alpha level based on the criteria. The n2y Library Guide document, located in the Teacher Reference Materials, provides guidance on each level. The document also provides guidance on Decodable Text and Differentiated Texts and includes a correlation chart. This guide can also be found in the n2y Library.