The first book in The Gentleman Bastard Sequence, a series of urban fantasy caper novels by Wisconsin author Scott Lynch, The Lies of Locke Lamora was published June 2006 and was a finalist in 2007 for the World Fantasy Award. In the United States, it is published by Bantam Books, and it is under the Gollancz imprint in the United Kingdom.
The novel is set on an unidentified planet with two moons, and there are constant references to the "Elders," the sapient species which inhabited that planet in prehistoric times and left behind mysterious architecture made of a virtually indestructible substance called Elderglass. The series focuses on a small part of the planet's overall geography, the Therin Throne Empire and the city-states which descended from it after the Throne fell from power. The events of this particular book are located exclusively in the canal city of Camorr, which is modeled after late medieval Venice.
Camorr is the home of two primary seats of power, one legitimate - the Duke Nicovante, undisputed ruler of the peers of the city - the other less legally reputable, Capa Vencarlo Barsavi, the king of Camorr's criminal underworld. Within this power structure, there is a "Secret Peace" which allows the peers and criminals to coexist without overt warfare between them: no thief in the city is permitted to rob an aristocrat on the streets, or break into their houses. Merchants, farmers, and all manner of lesser-ranked civilians are fair game, victim to both criminals in the streets and taxation from above.
It is on the fringe of this peace, and in direct and flagrant violation of it, that we find our protagonist Locke Lamora and his best friend Jean Tannen. These two, along with Calo and Galdo Sanza, Bug, and Father Chains, are the members of the Gentleman Bastards: a gang of con artists who prey exclusively on society's upper echelon, and who depend on the peerage's embarrassment at being robbed, to keep their nighttime activities a secret.
The Gentleman Bastards' motto is "Richer and cleverer than everyone else," and they worship a nameless deity, the Crooked Warden, who sits as the unmentioned Thirteenth outside society's conventional pantheon of twelve gods and goddesses. The Crooked Warden's primary mandates are, "Thieves prosper. The rich remember." It is in the name of these goals - a memento mori to the aristocracy, and the thieves' own benefit and joy at outsmarting the most powerful people in Camorr - that the Bastards ply their trade.
The Bastards are not, however, the only people who secretly stalk the Camorri night, or who can false-face their way into the most protected places and prizes, and the most significant conflict of the novel is centered around what happens when the Bastards' priorities collide with those of the Gray King, a man out for vengeance, and the Spider, head of the Duke's spy network.
The next book in this series is Red Seas Under Red Skies, followed by The Republic of Thieves. Four more books are projected for this series, but they have not yet been written at the time of this writeup.
If you have read and like The Legend of Eli Monpress, then I recommend this novel. The same goes in reverse: if you like The Lies of Locke Lamora, then take a look at the Eli Monpress novels, starting with The Spirit Thief.