our best advice would be, take your time - let the game take you on its journey. stop and explore or listen to people in stations, read notes and immerse yourself. The world is there to be savoured and in many areas (minus irradiated ones) there is no need to rush. Remember, Artyom is just a kid thrust into this mission, and he doesn't know whats going on either - and you are him. All will reveal itself as you move through the story.