I'm writing a futuristic light novel, in which the world looks really different than the world we're used to and thus I feel like I have to describe every single detail. However I won't really have space for that since it's a light novel, so i'm wondering if and how impotant the scenery would be in my case.
It depends on the story. Is the scenery important to the events of the novel? Does it actually have an effect on things? Does it change the outcome? If so, then yes, you need to describe it.
However, usually the scenery is not necessary to the story. In fact, scenery by itself is never necessary to the story. If the scenery is just scenery, there is no need to describe it.
However, scenery (or setting as it is usually referred to) is commonly used to describe the vibe of a particular place (ie, raining during a depressing/sad scene), or to act as a base to show a character's emotions (ie, showing how he sees the setting: "rejoicing in the brilliant sunrise," etc.). Occasionally you can show the same scenery twice, far apart in the novel, and demonstrate how a character has changed by noting how differently he now sees the same scenery.
So to make a long story short: decide if your setting serves a purpose. If it does, then describe it. Don't go overboard though. The description only needs to be enough to accomplish the setting's goal. If your setting does not serve a purpose, there is no need to describe it. You can drop one-liners mentioning the setting on the side (details always add a small measure of credibility to a work), but never focus on it.
I wouldn't describe in details if it is a light novel and has to be read easily. But I think that if the whole novel is set there then you will have the opportunity to be quite thorough. Just don't do it at once. Start with some basic facts and tell only what is needed and then as the story goes you can tell more. I think action is very important to make the story light so I'd include a lot of action scenes which use the specifics of that place - I mean you could use the different physics there, the different architecture, the different demographics etc. to make the action scenes more intriguing and also introduce the world to the reader. And to repeat Thomas - make sure that every information you give serves a purpose for the story. To sum up - what I am trying to say - make up of alternative ways to show the environment like action scenes and dialogue instead of just describing.