THE READABILITY OF ANY BOOK IS DETERMINED BY WORDS AND SENTENCES WHICH ARE USED AND WHICH VARY IN DIFFICULTY FROM EASY TO HARD. PRESENTED HERE IS A PROCEDURE BY WHICH TEACHERS CAN DETERMINE THE READABILITY INDEX OF ANY BOOK AND TRANSLATE THE INDEX TO GRADE LEVELS. THE METHODS EMPLOYED IN THE DEVELOPMENT OF READABILITY FORMULAS AND WORD LISTS ARE EXPLAINED. A BOOKLIST OF 139 BOOKS ARRANGED BY THE DEVEREUX READABILITY INDEX IS INCLUDED. SIX TABLES AND THREE FIGURES PRESENT DATA, AND A BIBLIOGRAPHY CONTAINS 18 REFERENCES. THIS DOCUMENT WAS PUBLISHED BY THE DEVEREUX FOUNDATION, DEVON, PENNSYLVANIA 19333, AND WAS REPRINTED IN 1965. (DF)