no im afraid not ...i often think the same .. a big fan i am and would want there to be more but no there isnt
if u think about it if there was another book and it told us everything we needed to know.. there wud be no mystery and like dumbledore "we are often left to solve things ourselves" which is what we must do then!
J.K rowling rote a great set of novels to reveal all secrets into the wizarding world .. wud be an offset to her BRILLIANT books.. although i am sad too, that their finished the 7 best books ever though!!
We can only hope that Rowling writes other stories. With Pottermore coming online this year, I'm quite interested in what she might be up to.