Description The Diphthong Decodable Reader Set is perfect for children who have mastered blending short vowels, digraphs, Magic E, R-controlled vowels, and beginning vowel teams and are ready to learn Diphthongs. This 3-book, 72-page set is the eighth installment in Charge into Reading s Decodable Book Series and focuses on the three diphthong sounds : AW, OW, and OY.