Do you need to play the entire Deus Ex saga to understand Deus Ex H.R.? [duplicate]

Possible Duplicate:
Should I have played the first game and/or Invisible War to fully appreciate Human Revolution?

I love Deus Ex 1, it is one of my favourite games.

But now a friend wants to buy Deus Ex Human Revolution, I told him to play the first two (well, the 2nd is awful) before playing Human Revolution, but he says that there are different stories.

Is this true?

As Deus Ex Human Revolution is a prequel to the series, it is perfectly appropriate to play it before the others.

I'm not sure this question is exactly a duplicate—the difference being "fully appreciate" vs. "understand"— but see this question for a very similar discussion.

In brief: no, you don't have to play the earlier games to understand and enjoy DX3, but if you have the patience to play DX1 in advance (IMO don't bother with DX2), you'll find DX3 even more enjoyable. I'm on my fourth play-through of DX3 and am still being amused and pleasantly surprised by references, both hidden and overt, to the original.