City of Stars by Mary Hoffman

Lovely, fantastical story, all the better for being partly set in a Medieval Italian (or, to be strictly accurate, Talian) town which holds a mad horse race each year - modelled on Siena, a city I have not visited - yet! This is the second book in the Stravaganza series. I was worried about not having read the first book, but this story of friendship stands on its own.