Fighters use the D10 as their Hit dice when rolling to see how many hit points they have when creating and leveling up the character.
I loved the CYOA books growing up, my husband and I are working out way through the recently published CYOA board game, it has a bunch of chapters that you work through.

Jason's book will be out on Kindle on August 1st-
https://www.amazon.com/gp/aw/d/B07S39J1NJ/ref=dbs_a_w_dp_b07s39j1nj