I have used these books with my four year old son.It must be said that they are very useful: not only am I able to test his blending skills, but he absolutely loves them. He is forever asking to read "those lift the flap books".
The level of difficulty seems to be about right, though perhaps one more book without digraphs would have been useful.
I have two criticisms to make, which have prevented me awarding these books 5 stars: they are too short, and the paper is too thin. It is actually possible to see the pictures without lifting the flaps, so I have to be very careful to cover the relevant side of the book when I'm reading with my son.
