"The book is about mice."
Translation:Het boek gaat over muizen.
This word order doesn't sound German to me at all. The German sentence would be "Das Buch ist über Mäuse." Just like the Dutch sentence, except in German we actually avoid saying geht in this case.
If you wanted to use over in the original, physical sense because the book actually walks over the mice, then in colloquial German you would say "Das Buch geht über die Mäuse drüber", with drüber reinforcing über. But I doubt that that's what you meant.