KJ Charles is a great writer, and this is one of her only series I'm aware of where one of the MCs isn't a raging blowhole. We've got Ned and Crispin, who certainly have their conflicts to work out, since Ned doesn't trust magic and Crispin is trying to unlearn so bad magical practices he was taught by his first mentor. They care about each other, and support each other, but they have their hangups and their insecurities and much of this is about how they navigate a relationship with each other given all these conflicts. That doesn't even bring into account that if the wrong person finds out about their relationship, they could end up in jail or hung.
Crispin finally finds a new teacher who is interested in helping use his magical abilities, and while this is a bit too close to the prequel's plot, there is a mystery involving the strange deaths of some rag and bottle store owners to help detract from that. There's a lot of tension built into the climax, and it doesn't just fizzle out afterward, since there are still other issues to resolve.
Since I've only read the first book in the Magpie Lord series, I only recognized Stephan Day from that series here. I'm sure there were others, but it wasn't necessary to have prior knowledge of them, or even of Day. If you know the other characters' backstories, you'd obviously get a lot more out of seeing them, but if you don't know then you're not going to be confused or lost.
I hope Ms. Charles writes more about these two. I love her writing, but since I'm allergic to her douche MCs I usually avoid her books. This series is the exception.