Mary Robinette Kowal 
Valour And Vanity 
(The Glamourist Histories #4)

Murano, Italy When a family celebration brings Glamourists Jane and David Vincent to the Continent, they seize the opportunity to voyage for Murano, to study the world-renowned glassblowers at work. But their ship is set upon by Barbary corsairs en route and they arrive in Murano penniless.Fortunately, they meet a gentleman banker who arranges for a line of credit and a place to live. But just as the Vincents start to relax, a solicitor arrives at their house and it becomes clear they have been the victims of an elaborate heist.Trapped, penniless, their safety in fragile shape, they hatch a reckless plan to get their money back. The ensuing adventure is a glorious envisioning of all the best parts of heist narratives, but in a Regency setting with magic.