Looking for a book from late 70s early 80s. Aimed at ~10years No title, no author info. Pages with text and pictures.
As I recall the cover was mainly black / Space background, with main character (teenager) on a skateboard in a surfing position. With a black jacket.
The story revolved around the teenager getting called and transported to help an alien race, one of the battles was with a rock monster.
It finished, along the lines of "Farewell, we may call upon you again.."