Wow! This is a hard one as these stories are super rare. I knew I'd seen one, and after losing myself into the sewer that is Amazon, killing the rabbit eared false leads, and skinning the champions of light that stood in the way of my diseased needs, I FOUND IT!
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This book by Miles English is just what you are looking for! It’s fun and pretty well thought out.
I wrote a urban fantasy / litrpg, and a lot of my readers have been telling me it would do really well with YA audiences. It's funny, light-hearted, and it's got some characters that I really think you're going to get attached to.
In another world, I must defeat the Demon King
Get it here: https://www.amazon.com/dp/B09W84B7FQ
And here's the blurb:
Henry’s life as a valiant defender of the realm is over—stolen away when he is transported to a strange new world. Instead of horses and swords, it has cars, rent, hamburgers, and a gun-toting part-time waitress named Shana. There isn't much use for a white knight atop a fiery steed… or is there?
Thankfully, Henry’s ability to level up and unlock powerful new skills hasn’t abandoned him. In fact, Shana is starting to level up, too. But there's a catch. Turns out, they’ve caught the attention of a secret society that's devoted to the very system of power that Henry was raised on. Led by the enigmatic Demon King, they aren’t happy about newcomers getting involved in their affairs. Magic, power, experience—the Society wants it all for themselves, and they'll happily kill whoever it takes to keep it that way.