For Grace Bonner, the bond of sisterhood is an exquisite, painful thing. In The Book of Atlantis Black, Bonner unravels the mystery of her sister and what happened in the final months before her disappearance, alleged overdose, and death.With access to Atlantis's email and social media accounts, Bonner attempts to decipher and construct a narrative around the circumstances surrounding her probable death: Frantic and unintelligible notes on Facebook, alarming images of Atlantis with a handgun tucked in the waistband of her pants, Craigslist companionship ads, DEA agent testimony, video surveillance, police reports, and various phone calls and moments-in-the-flesh conjured from memory.Through the construction and deconstruction of these materials and the history only she and Atlantis shared, Bonner finds questions that lead to only more questions, red flags that point in no particular direction, leaving her to decide how far she will go to understand a sister who, like the mythical island she renamed herself for, might prove impossible to find.