Is there any reason to get the N3 rulebook instead of the Human Sphere rulebook? I assume that the Human Sphere book is the most recent?
Don't buy any of the books if you're looking for rules. Just use the free ones you can download here. Spend your money on all the minis instead. Unless you want the fluff that is, which is meh at best and skippable.
Human Sphere is the first Expansion, it does not replace the N3 Core. The rules segments of both are available for free download from the Infinity site as mentioned above, and all the rules are compiled and updated on the official wiki here: http://infinitythewiki.com/en/Main_Page
