The Alchemist's Apprentice. The Zero Enigma, #5

A Stand-Alone Novel set in The Zero Enigma Universe ... Five months after the House War, the city of Shallot is on edge.  The Great Houses plot and plan against one another, while the magicians rebuild and the common folk fear another outburst of fighting.  And one young nobleman has a plan. Rebecca is a half-caste shopgirl in an apothecary, dreaming of an apprenticeship that will allow her to rise out of poverty and finally make a name for herself in a city that has no use for her kind.  But when her master undertakes a commission for an enigmatic young nobleman, she finds herself drawn into a maelstrom of criminals, ambitious nobles and a plan that may shake the foundations of the Great Houses themselves ...