With the reading and discovery books from Onderbouwd you learn to read in a playful way with the stories of Roos, Pim, Fem and Siem. The books are specially made for children in groups 2 and 3 and can be read themselves, but also read aloud. To make reading easier for young readers, there is a handy read-along card. There are also word cards to practice individual words. Each book contains a fun game with which children can practice the most important words in the book in an accessible way.

This app contains one book. Within the app you can purchase several books yourself, such as:
- Rose and the Chicken
- Rose and the Food
- Rose and the Sheep
- Rose and the Cow
- Lesson at Home
- Pim and the Football
- Fem wins Fish
- Fem to Zee

Substantiated Learning to Read is a product of Klassewerk publishing house. Another product of Klassewerk is Onderbouwd Online, a widely used teaching method for toddlers and groups 1 and 2 of primary education.