Human magic affects the connection of the soul to the body. Mermaid magic creates life. A long time ago there was magic that could reshape flesh. Not much is known about dragon magic since they live in volcanoes and don't really talk to humans. There's scholarly debate about whether the kinds of magic that exist are somehow related to the elements, and if so which set of elements. There's debate about whether all forms of magic are the same thing, whether they're the same as what the gods can do (and whether the gods are real, and there's a half-page digression into deism), whether they're the same thing as anything other than magic (like the way plants and animals reproduce themselves without mermaids carving statues of them), whether each species magic is actually one thing or several related things...
Different human magic traditions exist making use of different kinds of material components; mixing and matching has been tried, and doesn't do anything amazingly interesting. There are some rules of thumb for what components will go into what kinds of spells; one is that it helps if an herbal component already does something at least similar to the intended effect. Aiming works differently for spells that are prepared in advance, because of reasons that the book goes into.
Human magic can put souls in jars (they're not conscious while jarred), remove souls from jars, put people in new bodies, remove people from bodies, put people to sleep, numb body parts, blind people, deafen people, and facilitate the recovery of past life memories. Generally magically induced loss of sensation is temporary. It's a common side effect for people who have just had magic done to them to feel disconnected or unreal, or like the world around them isn't real. It usually goes away in not too long and is more common if the spell is done more sloppily.