Race Cars is one of 6 books in a set called Cool Rides, which is part of the Sound Out Phonics Based Chapter Books series. Cool Rides (Sound Out Levels 5 and 6) focus on the following skills: contractions, one-syllable spelling patterns, tense endings, word endings, compound words, prefixes and suffixes, and simple two-syllable words. Readers will not be able to tell that each book is written using controlled vocabulary.