This is a big sprawling epic fantasy, of the "poor street kid with no history is picked up out of the gutter and becomes a major player" type, rather than the epic quest type. There's something to be said for a story that takes the expected tropes, and plays them straight, if it's done well. And this is done rather well.
Summary: Azoth is a ten year old gutter rat, trying to survive, and to take care of the littles he loves, Doll Girl and Jarl and to keep them safe from his murderous guild leader When he runs across the legendary wetboy (a magic-talented assassin), Durzo Blint, he sees his chance to not only get out, but save his friends too, so he persuades Blint to take him on as an apprentice. He doesn't realise yet what that chance will cost him.
So, big and sprawling, yes. We follow Azoth from 10 years old, to over 20, and on the way we meet an enormous cast of characters, and following multiple plot threads. The worldbuilding is deftly done, set against a single city in a single country, but dropping numerous hints like little breadcrumbs about the rest of the world. There is a very real sense that this is one country in a world filled with many, with different cultures, architectures, magics, religions, but without overloading too much on the actual detail of any of it.
Plotwise, there's a whole lot of political intrigue going on. There's the council of the Nine, the underground organization who really run things, made up of people such as Momma K, the mistress of pleasure, who takes a cut of all the brothels - but takes care of them too, because she is of course the whore with the heart of gold. Then there is the monarchy, with the despised King who only thinks he runs things. Both are plagued with internal strife, as well as the ongoing vying for power between them, making this a place where nobody is to be trusted, and very few are who they seem, and everyone is manipulating everyone and everything around them.
There's also a lot of fights, mostly one on one, and assassin chases through the city. And one truly huge battle, but if you're after military on the scale of the Malazans, this is not the book to read. I knocked off half a star because for me, the cast is genuinely too big to keep track of, resulting in one character who we met early on, when Azoth is 10 and hasn't even met Blint yet, suddenly showing up again with a fairly pivotal part ten years later, and by then I'd forgotten who he was, or if we'd even met him before (at least until a pointed reference to that first appearance showed up). I really love that kind of thing usually, but somewhere here this one went just past my tipping point. YMMV, I might just have been reading this too tired and distracted to be really keeping track.
Overall, despite the heavy reliance on genre tropes, these things become tropes for a reason: they work, when done right, and here they are done largely right.
Recommended for: Lovers of intrigue, philosophising assassins, and morally ambiguous ... well everyone, except the King, actually, is morally ambiguous.
Not recommended for: Weak stomachs. Some of the violence is brutal, and quite lovingly described. And being performed by small(ish) children, against other small(er) children.
ETA: This is book one of a series, I didn't realise that when I picked it up, and somehow forgot to mention it here too.