I have read Metro 2034, the follow-up to Metro 2033.
One character from the first book is one of the main ones in this. The main protagonist in Metro 2033 does not appear in 2034, unless the shortly mentioned person with the same name, actually is the same character. This book is not as surprising and maybe not quite as good as the 2033 one. On the other hand, the 2034 story is in the same world, just a year later. Consequently, it follows the rules of the world, and speaks familiarity, rather than being an adventure in a, for the reader, totally new world. The 2034 is as well worth reading as the 2033 one. They should definitely be read in chronological order.
The Metro world is an open one, so there are many others who have written books based in it. I have not read any of them. I am not aware of any translations.
The first pages of chapter 14 contains someone's (maybe the character Homer) thoughts on what separates the "civilised" Homo sapiens from other animals. This is of course a very old discussion, and some of the usual distinctions, such as fire, speech and writing are brought up. The author (through the anonymous speaker in the text) arrives at a surprising conclusion. Animals, at least mammals, graze/hunt/gather food because they are hungry. When they had (this is especially valid for carnivores) enough, they are satisfied. Humans, on the other hand, fill their stomachs and then reach melancholia, and have to fill their mind with other stuff: looking at stars, arts, music, building, writing. Now, the idea that humans, when having tended to their basic needs, engage in "non-productive" behaviour is not new, but putting the melancholia in the equation is quite brilliant in my opinion. The "call", as the voice in the text puts it, can even be stronger than the call of hunger.
Metrro 2034 is a novel, so the melancholia idea put forward is not science. And the change from animal to the human animal did not occur in a jump ten thousand years ago, but the idea is interesting. By evolution, boredom occured, and then became an evolutionary factor in itself. I gather melancholia is not full blown depression, because that is not a drive towards activity.
If you can find the book published in any language you can understand, you have a great read ahead of you. If not, it seems Hollywood will make a film of at least the 2033 book. Let's hope they do not fuck it up.