Instruct: Classify the given review as either positive or negative.
Query: A good addition to the series, but darker

This was a good addition to the series, but the plot/theme change didn't seem to work as well. The action was slower-paced and darker, and the tension between the characters didn't seem as finely written as in the first three books. Overall it was a good read, but Riley's relationships seemed to take a depressing turn in this one - too much to balance out the darker tone and slower pace.