Rangers are an illustrated series of graded readers at eight levels. The series includes specially written stories, adaptations of novels and folk tales, documentary narratives and informative texts.
Each level from 1 to 6 introduces about 350 new lexical items. Levels 7 and 8 each introduce another 500 words, bringing the total word level for the series to 3200. The introduction of new words is carefully controlled and, up to Level 6, new items are picked out where they first appear. Other essential words relating to the topic are kept to a minimum and listed at the end of the book. Basic grammatical structures are taught within Levels 1 to 6, while at Levels 7 and 8 the learner discovers new ways of combining and connecting known words and phrases.