"Book 12b" explores Peter and Jane's mountain adventure in 131 new words, including 'goodbye', 'suggested', 'clouds' and 'discussed'. Once this book has been completed, the child moves on to book "12c". "The Key Words with Peter and Jane" books work because each of the key words is introduced gradually and repeated frequently. This builds confidence in children when they recognise these key words on sight (also known as the 'look and say' method of learning). Examples of key words are: the, one, two, he. There are 12 levels, each with 3 books: a, b, and c. "Series a": gradually introduces new words. "Series b": provides further practise of words featured in the 'a' series. "Series c": links reading with writing and phonics. All the words that have been introduced in each 'a' and 'b' book are also reinforced in the 'c' books.