I think Grimms Fairy Tales are pretty good for practicing German once you get into level 3. The langage is fairly simple and the vocabulary is limited. The german is a bit old fashioned but I didn't find that mattered.
There is a great site with all the stories with translations in more than 20 languages.
I tried translating English versions back into German (with a dictionary) to see how close I got to the German.
I also got an audio book from Audible - 50 Kinder und Haus Märchen
If you get a trial subscription you get 2 free books to keep.