DEEP ROOTS is the sequel to Ruthanna Emrys' WINTER TIDE and THE LITANY OF EARTH. It is a story set in a "perspective flip" Cthulhu Mythos. The basic idea behind the Innsmouth Legacy is the Cthulhu Mythos is not actively hostile but simply different. The Deep Ones are just another race of human beings, the Mi-Go are busy-bodies who want to make humans better, the Yithians (actually the Yithians are much worse). It moves the setting from the realm of horror into that of science fiction.
WINTER TIDE by Ruthanna Emrys is a book which came out last year, I read and I loved, but for whatever reason I didn't get to review. This is strange and an oversight on my part because it ticks most of the boxes for what I love in fiction: not only is it an H.P. Lovecraft-inspired story but it is also something that reinterprets the Mythos for a modern audience. Like Lovecraft Country by Matt Ruff or my own Cthulhu Armageddon, it's a work which tackles HPL's controversial elements head on and does something interesting with them.