An invasion from another dimension is shut down by an Empire's traitor and the world has a scant few decades to build the strength to resist a multidimensional Empire. How will the world fair when no one even knows its doom is one barred gate away? Fortunately, the traitor has a plan. Maybe with a bit of luck and planning, he can build a force to defend the world without anyone realizing it. 

Author's Thoughts:

What is litRPG

(From wikipedia) - LitRPG, short for Literary Role Playing Game, is a literary genre combining the conventions of MMORPGs with science-fiction fantasy novels.[1] LitRPG is a literary genre where games or game-like challenges form an essential part of the story. A LitRPG work simultaneously narrates the story of characters inside and outside of the game-world. At least some of the characters in a LitRPG novel therefore understand that they are playing a game: they are 'meta-aware'. So, while Tolkien's Lord of the Rings is a fantasy novel, a book about people creating avatars and interacting in a Lord of the Rings MMORPG would be a LitRPG novel.
Why do I read them? You know, I am not too sure. I love MMOs. I played them, quit them, joined up and repeated the cycle. They are fun! They are a massive waste of time but so are most games. Do I want to read about someone else playing them? Sort of?
The advent of VR and the possibility of VR someday becoming so immersive that you can't tell them from reality sets the imagination on fire. What if this could be life? But most stories fall short. At the end of the day the protagonist hangs up his VR helmet and goes to have dinner with his mom and dad or other family and it becomes meaningless. It's like the story that ends because the main character woke up and nothing you read matters.
There have been some books that explore the concept of the intersection of reality and total immersion VR. Enders Game is a classic. There were a few others that escape me but they exist, however, the cross between the game and reality is weak.
So what if the game was real? The technology needed for total immersion VR is so advanced that by the time we reach that goal technology should have naturally evolved to include several items.

You must have direct neural input. You simply can't have a total immersion (all senses and perfect presence) experience without this basic prerequisite. If you have direct neural access, you can probably do neat things like feed knowledge and skills directly to that person. You can undoubtedly do many horrible things as well. Muscles are controlled by the brain. If you control the brain why would you let the body just sit there and rot? A person that sits unmoving for 24 hours a day will have their body whither away just like a coma patient. However, if you control the brain you could control the muscles. On a basic level, this would be isometric impulses, working muscle group against muscle group to avoid atrophy. Taken to its logical conclusion you would be able to gain muscle mass and program muscle memory. The flip side is that you could remote control their body... but let's not go there.

So what would people do if it were real? Well, they would probably limit and regulate it since the drawbacks are very obvious. Even if you look at the basic aspects of this you can see some negative possibilities. Look at the Sword Art Online anime. Personally, I think they missed the boat by putting a bomb in the VR helmet. Do you really need a bomb when you have direct access to the brain?
So what kind of events would you need to have a situation where the obvious drawbacks haven't been explored? Maybe a society where the advancement of technology has so far outstripped the explorations of its applications that ignorance was truly bliss? Okay, so I had to put in an alien invasion to kickstart the premise, but that was just one of the possibilities.