The anime goes further than this did anyway, this covers maybe season 1? Season 2 of the anime roughly covers the rest of the novels, but also has differences to it including how it ends, so might be worth a look at the novel volumes for comparison.
I'm not that familiar with the novel version, but the anime has a "happier ending," according to someone who did read them. I don't even remember how the anime ended by now, might be time to give that another watch. I just ended up here today 'cause I remembered a funny line or two Chaika said, and got curious since the manga wasn't finished last time I looked either.