Almost everyone on Earth has already read the Harry Potter series, which is fine. I encourage it. But it upsets me greatly when people who haven't read the Harry Potter series dismiss J.K. Rowling as yet another YA author who is too famous for her own good and whose writing career is motivated by a desire to pen the next cash cow franchise. I doubt very much that Rowling ever could have imagined the eventual pop culture saturation of her series, and its popularity in no way diminishes her incredible skills as a writer and storyteller.
The Casual Vacancy, her first non-HP novel (and her only novel for adults (published under her own name)) was so highly anticipated when it was finally published that it was naturally dragged pretty thoroughly by critics. The bad reviews became the only thing anyone knew or remembered about the book, which was especially disappointing to me because I read it and although it was far from perfect (especially the ending, which is pretty rocky), I really enjoyed the experience of reading it. That is to say, it suffers from some bad narrative points and plotlines, but it is incredibly well-written and the character development is stellar. I felt like I could have continued to read about these characters doing really mundane things for hours. It is not the greatest book I've ever read, and it is nowhere near as strong as the HP books, but it really is pretty good and didn't get a fair shake.
Thus, the Robert Galbraith books, aka the J.K. Rowling books published under a pseudonym and very well-reviewed. Thriller/spy novels fall into a distinctly guilty pleasure reading category for me, so I haven't read these yet and I'm waiting for the perfect opportunity, like a long flight, to finally get into them, but everything I've heard about them is overwhelmingly positive.
And for those who just can't get enough of the HP stuff, Rowling recently published a series of short stories on her website Pottermore that expand on existing characters. Along with several spin-off movies she's writing and the Tales of Beedle the Bard (a companion book she published as a fundraiser for her favorite charity), she clearly isn't ready to leave the HP universe behind, which is fine with me.