English Grammar in Use
A self-study grammar reference and practice book for learners of English, written by Raymond Murphy and published by Cambridge University Press. It is built around a simple format: each topic gets a two-page spread, with a clear explanation on the left-hand page and exercises to practice it on the right. Units cover verb tenses, conditionals, articles, prepositions, and more. Often called the blue book by students and teachers, it is meant to be dipped into by unit rather than read cover to cover, and it is one of the most widely used ESL grammar books in the world.