The Medusa Plot by Gordon Korman

This book pits Amy and Dan Cahill and their remarkable family against another group, the Vespers, who kidnap a number of Cahills in order to motivate Amy and Dan to steal a painting from the Uffizi Gallery in Florence. I appreciated that Dan's friend, Atticus, pointed out the morally questionable nature of the Cahills' actions. I like all the history that's worked into these stories, although they rely a lot on technology to get them out of tight situations.