I want it because it is linux and looks interesting. But do I need to have played the previous games to understand it? They are all windows game.

cant you play the first games with a win-emulator? if its possible i would recommend it.

my opinion: yes, you will understand enough. of course you would understand more about the actors and their reasons with the knowlage of the first two games.
theres a "what happened in the previous episode" clip in the game too, so the main story should be clear. but for me the quality of the game is not only the story.
but maybe you need an answer of someone who dont knows the first games.

while i enjoyed the graphics and characters, i hated the world and unrealistic movements of the characters. from a story point of view, i haven't played the previous games but i have played this game twice...and i have absolutely no idea of what is going on :(