whatever_dude summed it up pretty well. It's not without its faults(terrible checkpoint system), but the single player is nearly a perfect game. Perfect pacing, smooth and engaging gameplay, the executions don't interrupt the shooting, the weapons feel amazing, tons of customizations and upgrades, the secrets are so well done they make you want to find them, and top it off with a KILLER soundtrack. It's all about action, no nonsense story, or cutscenes. Back to raw gaming. It's just overall the best FPS game I've played in at least a decade. It's THAT good.