This wonderful little duology doesn't have a proper series name, but both volumes do have the words 'the deep' in their titles, so that's what I called it. In retrospect 'Mermaids With Teeth' would have worked as well.
Mira Grant (the pseudonym of urban fantasy author Seanan McGuire) tends to be better known for zombie fiction (the opening volume of the Newsflesh series; Feed, is what I describe as zombie fiction for people who don't generally read zombie fiction), this was her first foray into something that wasn't living dead.
Rolling in the Deep is actually a novella, and the two books can be read independently of each other, although Into the Drowning Deep does contain some pretty major spoilers for Rolling in the Deep.
The premise behind the book is that the Imagine TV network (a fictional company that is kind of like a cross between Syfy and NatGeo) sends out a ship filled with reporters, scientists and performers in the guise of proving whether or not mermaids are real. Unfortunately for everyone concerned they find the answer to the question.
Into the Drowning Deep takes place 7 years after Rolling in the Deep and has a different group, a much better prepared one, and they seek to answer the same question, with equally dramatic consequences.
The first book is close to perfection. It completely captures the feel of a mockumentary and it drags the reader into it. It's also a total page turner, just as well it's relatively short, because once someone has started this one, they are literally unable to put it down until it's done. Although short it draws it's characters well and completely and makes them connect to the audience. It's so well done that when I'd finished it I was disappointed and a little surprised to realise that the channel and the mockumentary that they set out to create didn't actually exist. The series as a whole has been optioned for a filmed version (whether or not it will really happen is anyone's guess), but I honestly think they could just do Rolling in the Deep as a one off and it would be a stunning piece of TV. It would require next to no adaptation, either, its that well written.
Into the Drowning Deep is the inevitable sequel. It's a full length novel that use it's extra size and word count to delve deeper into the mysteries that were only hinted at in Rolling in the Deep and to examine the further reaching consequences of actually achieving their objective to prove or disprove the existence of mermaids.
Mermaids have in recent times become one of the monsters du jour. They feature in the TV series Siren as well. However the modern mermaids are nothing like Ariel. These things are vicious, cunning, sea creatures that are used to fighting for survival and don't like any incursions their territory.
I don't know if Grant intends to add to these two slices of horror, but I'd be onboard if she does,
