From Will Wight- A delightful series and my personal all time favorite. As a bonus Will is very active and interacts with his fans on a regular basis. I'm not ashamed at how many times I have read his books, but i'm still not going to share the number.
The Arinthian Line
Sever Bronny is very talented and does a fantastic job telling a story without becoming overly wordy. If you're in the mood for an epic adventure. This is for you. This series is complete and he finishes his next series later this year.
Challenger's Call Series
Nathan Thompson writes a fun story that touches all your feels. This is the first book I read that was a LitRPG and thoroughly enjoyed it. His other series that he is working on is a cultivation series and it is just as good! I have loved and impatiently waited for the next release since the beginning.
As a side note, I don't think I would let my kid read this series until he was older. There are some adult topics that might be hard to explain to a ten year old, as well as some mild language.
The Divine Dungeon Series
This series has been complete but Dakota Krout is still building on this fantastic world. I have yet to read one I didn't like. His writing style is effortless to read and his story engaging.
The Green Ember Series
Fun for the whole family! S.D Smith recently finished this series. Each book leaves you excited to read about what happens next.