Quite a weird series. It started as a silly and light-hearted read, but oh boy does it get dark occasionally later on.
While having below average quality of the prose, it is surprisingly well thought-out thematically, being one of the few series where "no killing" policy actually does make sense narratively. It also has a whiff of persian mythology, which is pretty rare in LNs.
It is also complete at 6 volumes, reaching intended stopping point.