The "English Grammar in Use" series, a collection of grammar books by Raymond Murphy and published by Cambridge University Press, is structured into three main levels, not three separate levels for the elementary book. The three main levels are Essential Grammar in Use (elementary, A1-B1), English Grammar in Use (intermediate, B1-B2), and Advanced Grammar in Use (advanced, C1-C2). The Elementary level book is titled "Essential Grammar in Use" and is designed for beginner to low-intermediate learners.