In a sense, all fantasy derives from the vast number of myths developed throughout human history. Nature's force and fury, death, disease and prosperity, the fearsome dark and the blessed day were all given meaning through the gods and monsters of every culture's mythology..
Almost every character that is not human will have a magical, supernatural, or mystical aspect.
This varies according to the story and number of characters. The complexity of the gods can be quite high, while the humans are little more than lightly-drawn pawns; or the humans are complex enough to drive the actions of the gods.
The books can be very obtuse, but similar to folklore, legend and myth, meaning exists at all levels. Readers with a background knowledge of the mythic traditions will enjoy the stories most.
Violence is generally low, similar to traditional mythic tales. Some lightning-bolt-throwing, perhaps drownings at sea or earth-swallowing occur.