The Smoke Thief by Shana Abe

Dubbed the Smoke Thief for a series of daring jewel thefts, Clarissa Rue Hawthorne didn't expect the drakon leader himself to come to London dangling the tribe's most valuable jewel as bait: the Langford Diamond. But Christoff, the charismatic Marquess of Langford, had to catch Clarissa before anyone else did - or risk exposing the entire clan to the world of ordinary mortals. He never expected that the outcast halfling he pursued would have a proposition of her own to save the drakon - a proposition so dangerous, so tempting, that Christoff will find it impossible to resist: to join forces with her. 

A light, enjoyable read.