Imagine the Assassin's Creed video games, minus the ridiculous “genetic memory” framing device. Now add in a medieval setting and a pinch of magic. Bang! You've got The Night Angel Trilogy, also known as The Shadows Trilogy, by Brent Weeks. These three paperbacks have been flying off the shelves since their introduction in 2008.
The protagonist is Azoth, a pickpocket orphan (man, there's a lot of them running around the fantasy genre) living in the streets of Cenaria. The boy becomes an apprentice to the best assassin in the city in hopes of avenging the rape of a childhood friend. Cable viewers who want blood and sleaze in equal amounts (I know you're reading, True Blood fans) couldn't hope for better source material.