I'm so glad to hear you liked Cuckoo's Calling! It's on my TBR list. I've been avoiding reading J. K. Rowling's other books because I'm afraid I won't love them as much as the Harry Potter books.
I definitely get that feeling. I know a lot of people didn't like The Casual Vacancy (although I actually did), but as far as I can tell, people tend to like the Cuckoo's Calling a lot more. It's definitely entirely different from Harry Potter, but I think that you have a really good chance of liking it if you enjoy mysteries.