This book introduces three new letters 'b, i, x' in five new words so that children can sound out the letters and blend them together in the new words.
The process is known as synthesizing, and the teaching method known as 'Synthetic Phonics'.
The letters introduced are the same as those in the A Series, book 2.
Four new words 'bat, bin, tin, hit' have been added to this book to make sure that each particular sound (phoneme) and its letter (grapheme) are learnt by the children before moving on to book 3 in the A or the B series.
The only connecting word in this book is 'in'.