It's actually a prequel (if you're talking about Human Revolution, and not the handheld title). I only played Deus Ex: Human Revolution and think the story holds perfectly on it's own. There's some background lore, from what I understand, that is common to both titles (corporations, groups of people, etc) but in no way relevant to the main story.
That said, whenever I enter into a series of games without playing the first titles I always read the plot synopsis on wiki, if it sounds like you're supposed to know something already. Not needed to enjoy this game at all though.