Read with Biff, Chip & Kipper are one of the more commonly used reading books in primary schools. Both my children are using them as their take back homework to read each night. The books start from level 1 to 6 and gradually increases in numbers of words and complexity by level. Some of the books are with phonics.
In addition to the books they read at school, we had also bought a full set of the books too. I find the books are very applicable and helpful for both of my children. We love the paperback books, but I welcome the use of a book app for whenever we go on holidays or outings. Less hassles with misplaced books and of course less weight to add to your luggage!