Gundam 101: Navigating the Gundam Universe
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http://www.animenewsnetwork.com/feature/2015-10-21/mobile-suit-gundam-where-to-start-and-what-worth-watching/.94461
While the latest Gundam series, Iron Blooded Orphans, stands alone from the rest of the Gundam universe, you might still decide it's time to take a look back into the nearly four decades of Gundam lore. With a main Universal Century universe and multiple stand-alones, it's a tangled mecha-web to unravel, but the Anime News Network gives it a valiant attempt, including a quick guide to which series are worth your time and which can safely be left powered down and mothballed.