I first became acquainted with Andre Klein's German language stories with Peter und das Huhn, one of a series of stories that lets language learners practice their skills on simple amusing stories. Bert das Buch is an engaging tale of a book who goes on an adventure. The pictures are much better in this book than in his previous books. The story is easy to follow and engaging for even someone like me, with minimal competence in German.
From a composition standpoint, the text may have rushed a little bit toward the end, and become a bit harder to follow. But it is also good to have a section that you have to push yourself to understand. It's still a fun book that I have read several times. When I am tired of studying German grammer, I often pick up a story in German for relaxation with a bit of practice. These stories of Andre Klein's: Peter und das Huhn, An Ocean Adventure, and Bert das Buch are right at the level for a beginning German student. I think they are well worth purchasing.