I have no idea how it ends, but everyone I saw talk about it seems to like it. Sometimes it's ok to have a manga that is short and sweet.
Also usually mangaka do plan for wrapping things up in 2 volumes in case the serialization doesn't work out. It's really only really naive mangaka that set up way too much too early that get unsatisfying ends in a short run. Axe-kun is more of a problem when it hits a series that has been running for a while and the mangaka has established long-term goals and arcs that have to be abridged or abandoned.