While I would describe Brent Weeks's trilogy as a fast-paced, easy read (comparably), don't take that to mean its content could be mistaken for Young Adult. It is dark and gritty and pretty gross at times, the story starting out describing the cruel reality of the life of orphans living in the city slums. The streets are we meet Azoth and learn exactly why he decides to take on a new life as Kylar, an assassin (or "wetboy" as its named in this series—though the name may not sound as dangerous as "assassin", trust me, they are). The book does hop around to different character POVs, and while sometimes you might feel like the story got interrupted, I take that as a good sign to show how engrossed you get in Kylar's world, not wanting to leave it. Excellent pacing and character development. It will keep you guessing and you'll feel the need to keep reading to see where the characters end up. Durzo Blint is also one of the best of the archetypical tough mentors out there, and for many readers, he ends up being the favourite.
For Durzo Blint, assassination is an art-and he is the city's most accomplished artist. For Azoth, survival is precarious. Something you never take for granted. As a guild rat, he's grown up in the slums, and learned to judge people quickly—and to take risks. Risks like apprenticing himself to Durzo Blint. But to be accepted, Azoth must turn his back on his old life and embrace a new identity and name. As Kylar Stern, he must learn to navigate the assassins' world of dangerous politics and strange magics—and cultivate a flair for death. More on Goodreads.