There were quite a few adaptions of the Harhi franchise. The original series of light novels, twelve or so of them currently, were adapted into a manga which is currently on-going with ten volumes released. Then came the first season of the anime which was based on the manga. Apparently the manga deviates from the light novels quite a bit which would explain the fact that the anime virtually ignores the plot of the novels. The anime also had a second season and a movie produced for it. Will there be more? I don't know, they certainly have enough material to continue the anime. This topic isn't about that.
Which version of Haruhi do you like the best? Have you only seen the anime or read the manga? Have you been exposed to multiple versions and have a favorite out of all of them? Are you curious to view other versions of the series now? I've seen at least a little bit of all three versions and I have to say the light novels are my favorite. They explore the universe and characters more in depth than the anime or the manga. It's also much slower paced than the other versions: remember episode 0, where the crew tried to make a movie? That was the entire basis of the second novel.
So, pick your favorite. And if you haven't ever heard of this series I command suggest you check it out.