In time for Halloween JKR gave us another short story (more background info to be honest, it's not like it has a plot). You can read it at Pottermore (if you have an account and can actually remember your user name and password) or you can read it here:
J.K. Rowling writes Harry Potter Halloween tale profiling 'malicious' Dolores Umbridge My personal take on this little story is that it's wholly pointless. It just repeats that Umbridge was always a nasty person with no depth to her and she's worse than blood purists. Nothing really new or insightful is revealed, nor do I believe did anybody care to know this sort of stuff about Umbridge. I also found it very unbelievable that anybody would buy her claims of being a pureblood, considering how small the wizarding community is. And of course she was a Slytherin, because where else could an evil person in HP have come from.