Read the novels here
Trailer, as well as summary to the story :
It's a lot better than .hack in my opinion. In addition, if you were to argue over originality, the original web novel for Sword Art Online predates .hack. Anyway, if you're enjoying the anime then I'd highly suggest you try reading the novels, as for any anime that's based on a novel, such as Index. Though if you're enjoying the anime as it is and don't want to be spoiled on what happens next, then that's fine to. For the most part they're keeping very true to the novels, and whatever changes they make barely affect the main plot at all.