Learning about two IRL premises in this book caught and held my attention: 1) A real ship from 1773, found buried under the rubble of the World Trade Center, and 2) twin-to-twin transfusion syndrome.
Zak hears a voice warning him of danger, and when it saves him and his friends Moira and Kahlid from the subway as it fills inexplicably with sea water, he decides its his guardian angel. He pokes around in his parents' room and safe and discovers he had a twin brother, Tommy, who died when they were two due to TTTS. His parents and a therapist inexplicably hide the boy's death from him and pretended all these years like Tommy didn't exist.
But now Zak's having ...visions? experiences?...of the subway filling with water, and no one else can see them. The voice lures him and his friends back to the subway and they slip through a breach into another world, a parallel universe where magic rules, Moira is in danger just because she's a girl, and Zak can finally talk to Tommy's ethereal form.
They learn the voice was not always Tommy, but another man's ghost, and he has plans, horrific plans, for our world...
I won't spoil the ending. Just know that while this book features a 12-year-old protagonist, it's just creepy enough and deals with some brutal enough treatment of women (sexual abuse is implied but never outright stated) that I'd recommend it for young adult, not middle grade.
