Scale - Greg Egan

When electronics importer Cara Leon goes missing, private investigator Sam Mujrif is hired by her sister to investigate. Cara is eight times taller than Sam, but evidence soon points to players much smaller than either of them. As Sam and his cross-scale colleagues pursue the case, it becomes apparent that Cara's disappearance is linked to the development of technology with the potential to reshape their whole society, and radically alter the balance of power between the scales.