I have a collection of Open University German workbooks from when I did my degree.
It's been a few years since I looked at them now, so I am just clinging on for no reason.

The top row is beginners German alongside accompanying cd's.
The second row is intermediate German.
The third row is Upper intermediate German.

They are brilliantly written (as all OU books are) and are top learning resources. Hopefully, they can go to someone who is studying German or interested in the language.

Just a note - they do have some of my notes scribbled on the pages.

Open University German workbooks - 3 levels (Skipton BD23)