This is a review for the second book in the Russell's Attic series by SL Huang.
I really liked the first book in this series (Zero-sum game), but unfortunately the second one does not reach the quality of the first. At the beginning, the story is very slow-paced and tedious, but it picks up in the second half. However, at that point the overall story arc also becomes rather predictable (in short, Cas builds herself a little team), and the details of the plot do not make much sense on their own (you often wonder why the protagonists do what they do, and the only explanation seems to be that this is necessary to support the overall story arc). Also, there is one resolution of a sub-story (the Mafia stuff) that just does not make any sense at all.
While I liked Cas' special abilities in the first book, here they've become just a tad too surreal. For example, Cas' is supposedly able to plan a certain mission down to second accuracy days in advance (and then worries when she's a few second behind the plan), when the very same plan involves human guards that are patrolling the area (which are certainly not going to conform to schedule with second-accuracy). Often, it feels as if the author was desperately trying to one-up on Cas' abilities of the first book (which I felt was really not necessary). Cas' sudden reluctance to kill just because she's got some friends who don't like that (even though she's not quite sure what friends actually are) is not plausible either.