I am unsure where to start here, because boy, did that take a turn! I really enjoyed A Monstrous Heart, but always felt a little like I was playing catch up as I read, feeling my way through a new world, with a seemingly complex 'magic' system. By the end I had it figured out and it left me wanting to know more. The Deepwater King picks up almost immediately from the end of book one and doesn't let us. Arden is duped and tricked more times than any person should have be, and by people who are meant to be friends - she discovers something huge (but totally spoiler-y), which alters her path, and to get what she wants she has to visit places and people she'd desperately rather not. The story picks up again at about 80% in, and if you've not already been dragged down to the Deepwater Kings palace, you will be - and you will need the final instalment to bring you back to the surface and I would love to say more - but I really can't without spoiling it! Just pick it up and read it!