Well this was the 1st Killzone that I played and for knowing less of the lore, it gave me very good moments the gameplay is the best for the PSP console I mean wish there is more games like this that system kinda like Isometric and 3rd person shooter it's the best way to mantain a player like me stick to the console, the story it's not bad XD, well it's kinda like it's own story but just more than the usual ISA vs Helghast and there is a traitor, but besides that a jewel for the PSP.
PS: It's not hard to play the last episode, heck there is plenty of tutorials with the archive linked.