It's a unique, fun and wonderfully lighthearted story, with interesting twists on your classic RPG tropes and monsters. I loved it and the characters so I much ended up reading the manga as well.
That said, going in to it, be aware that it is NOT a fast paced, action-centric shonen anime with 30 minute fight sequences. Because that seems to be the only thing people leaving poor reviews wanted. It does have fights and gets more intense as it progresses, but it is not that kind of story.