I think the Waterfire series is a good read so far although it can be a little bit of a let down when some things are not resolved at the end of a book since it's a 4 book series.
Serafina is a mermaid about to be declared fit to rule her kingdom and be betrothed to a merman from another kingdom when her kingdom is attacked before the ceremony can be completed. Serafina is forced to literally swim for her life while trying to figure out who is behind the attack on her kingdom, if her betrothed still loves her or is just going through the motions because their kingdoms demand it, and the meaning of mysterious, repeating dream that may hold the key to saving the entire world of the merpeople. She has to figure out who she can trust and who will betray her.
There is a lot of mythology in the book and also a lot of made up words but after a while you get used to it and there is a glossary included in the back. For example the merpeople speak Mermish and call humans terragoggs. One really interesting thing is although they are merpeople a lot of them have other sea creature bodies such as crabs, eels and whales.
Ponyfan