The language in graded readers is restricted in terms of both vocabulary and grammar.

The vocabulary is indicated by the number of headwords. This means a restriction on a standardised set of common words, but excludes any specialist vocabulary needed for each particular story, and explained there. As you can see from the tables below, the number of headwords in a level varies from publisher to publisher and even - with the OUP - between different series by the same publisher.

Grammar is carefully graded too. Each publisher gives a summary of the grammar structures introduced at each level.

Graded readers allow you to read quickly and enjoyably, and to revisit a lot of vocabulary. Many also come with audio - on either CD or cassette. Worksheets and/or exercises are available on-line for teachers, but there is no reason why you should not use these independently.

Graded Readers aimed at younger students are outside the bounds of this survey.

More fluent readers can try ungraded and unabridged (nothing removed) texts. OUP's unabridged collection is called
Oxford Bookworms Collection.

Oxford Unversity Press publish several series of readers, both graded and ungraded: OUP readers page

Bookworms Library is the biggest series, with over 130 fiction titles. The introductory level is called Starters, and has its own page. There are also two additional series under the bookworms umbrella: Factfiles (see below) and Playscripts (outside this survey). Instead Storylines and Oxford Progressive English Readers are both outside the grading system of 'bookworms' and are covered below.

Genres: crime and mystery; thriller and adventure; fantasy and horror; classics; true stories; human interest.
 

Bookworms Factfiles: non-fiction.
 

Storylines: original contemporary stories.
 

Progessive English Readers (OPER): adapted classics.

The 5 grades are roughly equivalent to Bookworm stages 1-6.
 

Penguin Readers come in seven levels. There are extra series aimed at business readers and young readers.

Many can be bought with audio.

Genres: adventure; animal stories; auto/biography; business world; crime/mystery/spy/thriller; cultural & social issues; ghosts/spine chillers/horror; non-fiction; plays; romance/historical novels; science fiction fantasy/future; short stories; teenage appeal.
 

All titles are fiction, modern and international, with a diversity of genre, and all can be bought with audio.