My Sister, the Serial Killer

Not sure if this is the right fit?

Consider And Then There Were None by Agatha Christie. Recommended by 3 sources.

“Starts like a social parlor game that hardens into a sealed-island murder puzzle: ten strangers, an accusing recorded message, and a steady body count keep momentum tight. Main value is the hair-splitting plotting and the intellectual pleasure of spotting and checking clues against the solution. Main limitation is thinly sketched characters and a schematic moral tone, so emotional depth is secondary to clever mechanics—readers who want soulful characterization will find the cast functional rather than lived-in.”