Peter and Jane books were designed to get children reading. The series of books used the repetition method of teaching, introducing new words slowly, ie.:
Peter and Jane
Jane and Peter
This is Peter
This is Jane
... you get the idea!
I can remember a dog, a tree, a ball and 'Mother and Father' being involved somewhere too.
There were 36 Peter and Jane books in the series: 12 themed stories with 3 levels in each theme.