Understandable. If/when we see Season 2, we will have A LOT more on Eleonora, i hope we do.
That’s the problem with ongoing stories, it doesn’t help much the anime-only people when told “Yeah, what you want to see is on Book X which might never be adapted to anime”. And in this case it HAS to be on the books because the manga is behind the anime, the novels are the ones multiple books ahead of both.
I do still recommend going to the books though, up to at least Book 3 which is my favorite of what we have so far.