There are a few things that really differentiate
Career of Evil from the other Strike novels. One is that the driving thread of the book is
not justice for the victims (as it was in the first two books) but the threat against Robin. This gave solving the case a real sense of urgency -- we don't want our Robin to be in danger! Also in this book, no one hired Strike to find the killer, he was doing it because he was personally involved in the case. The other big difference is that this is the first Strike novel to provide chapters written from the killer's POV, which (among other things) gives readers a much better chance to figure out the killer.
So, did these changes make me like this novel more than the others? I'd say Yes, particularly the chapters with the killer's POV. I think it was an effective way to draw me deeper into the story and really want to try to figure out the identity of the killer. I'm not completely certain that I like
Career of Evil more than
Cuckoo's Calling, because there's always a soft spot for the first one.

I surely liked it better than
The Silkworm, though. I still can't get over how gruesome the crime scene was in that one, and I didn't find
The Silkworm's characters as relatable as in the other two books.