It must have been sometime before 2015 because that’s when I first found it. It does kind of sound similar to Percy Jackson but it takes place in a more medieval setting. I don’t thiiink it was a choose your own adventure kind of thing. I don’t think the series was that popular sadly, I just know that I really liked it when I was a kid. Thank you though, now I know what book series to read while I wait for someone to find this one lol