This book series by Daniel B. Smith provides an impressive and invaluable collection of English Grammar multiple-choice exercises. The books cover different subjects such as word order, articles, verb tenses, active and passive voice, phrasal verbs, prepositions, nouns, conditionals, reported speech, confusing words, word formation, and idioms. The series has different levels of difficulty, from Beginner to Advanced, and is aimed at enhancing your English language skills.