Lots of readers figure out the killer on this second book. There are some clues that are easier to “click”, unlike the other mysteries in this series. For me, it was the strong acidic smell on the crime scene, which I knew could give someone respiratory problems, at least for a while.
The tough thing to figure out is the book, though.
More words = more specificity.
It’s like painting. You can do it using only primary colors without mixing them at all or just do it black and white. Or you can use all sorts of tones and shades, to achieve your result.