what was good in the first book was still good in the second, and what was bad still was. 

the mystery is still good! i mean, the murderer was obvious since the beginning imo and the explanation/motive/course of events disappointed me a little but the clues that lead to their discovery were really cool! and there are still some threads going on, which proves how rich a story it is. 
on the other hand, i'm quite sad that

the truly devious letter was a scam and that the two students were not important at all in the end. i did not really see the point of having them have such an important part in the novel. i understand that it was meant to lead the reader on but it left me wanting more.

 

as for the bad stuff: the marginalised characters? still marginalised. almost unnecessary. plus, the past events were really repetitive in the way they were told. and what was happening with david, and his relationship with stevie—it was all very corny. i don't have a better word for it lolol. like, the way he's described through stevie's eyes, the way he acts, i don't feel it at all (except for his dressing up as BBC Sherlock. i have to give kudos to that). i hope it was done on purpose and that they'll end it in the third book bc otherwise, huh. 

other than that, it's still a page-turner, the author really knows how to leave the reader standing on edge!