Dutch books (for children) use the ‘AVI’ system to indicate the reading level. The system is structured: the higher the level, the more difficult the vocabulary in the book. The levels are:
- avi s/start (learning to read)
- avi m3 (reading level required in the middle of 3rd grade)
- avi e3 (reading level required in the end of 3rd grade)
- avi m4
- avi e4
- …
- avi m7
- avi e7
- avi p/plus (reading level required in 8th grade, end of primary school)
For comparison, this is what Avi start looks like, the left page is written on average e5 level.
I don’t know if you are located in the Netherlands, if so, the libraries have dedicated sections for each of the Avi-levels, the librarians can show you where to find them. Also online you can find many lists of recommended books for each Avi level. Once you are comfortable with one level, move up to the next level until you have reached the end. By the time you are comfortable with e7 or plus, you can safely grab any other book you can find!