With the bits and bobs of a local supply store (and sometimes not even that) pretty much anybody can step to a world, almost, but not completely, identical to our own, but untouched by civilisation and they can keep on stepping to limitless new worlds. Unbounded resources, space for everyone and suddenly we have the ability to move anywhere in four dimensions. People can stroll through an outer world and the step back into the middle of a closed bank vault. People rush to push new frontiers, create new lives. What is a country when that country stretches through thousands of universes? How do we change when suddenly a whole new layer of life is given to us? When faced with all this choice, what do people really want with life? When they can have all the freedom and space they could desire at a snap, is there still something worth having in living together and the earth as we know it?
The idea is intoxicating and powerful. Most of the story doesn't deal with this, crime is handwaved as largely unnecessary as overcrowding resides. Our protagonists can show a frustrating inability to realise that they can step out of danger rather than run. The scope is frustratingly small, apart from the US the only country we get a glimpse of is England (not even the UK as a whole). Apparently lots of them have abandoned the first earth. But I've lived in a small town and people want friends and people and nightclubs and convenience in commuting. The UK is a cynical country and we would realise that running through the forest for food and throwing up before clocking into work is a novelty, ultimately inferior to popping into a supermarket and a 15 minute journey on the underground.
The story isn't how we would react to a change of situation, because other things are weird too, sentient AI, strange creatures. We have an adventure story, exploring the peculiarities and stepping to more distant worlds that people have never reached before, looking for answers, down the rabbit hole. But with more weight than usual, because Earth has changed too and the rabbit hole may end up directly having something to say with our existence. There are a lot of pop-culture references which prevent something from seeming more important than the culture that birthed it and the story is incomplete before the inevitable sequels. Expectations weren't met, but the replacement is amenable.