I really enjoyed this /little gem/.
It definitely felt like an early reader, in that the plot was very simple and short, but for a pocket size adventure I thought it worked really well.
It wasn't particularly developed, and as the reader I don't feel I learnt a lot about the characters, so if that's a big thing for you it might feel underwhelming.
But, even so I really enjoyed the short but wild ride. It felt almost like a small but intense rollercoaster - not exactly the most thrilling, but I would definitely ride it again and again.

I could easily imagine a longer series of adventures with these characters that properly fleshed them out a bit more, and I am particularly of Melanie Demmer's art style.