And volume 23 just came out in English yesterday! Volume 24 comes out in October and vol 25 comes out in December, so you can actually read the full main storyline before the end of the year. Vol 26, Redundancy, is side stories and an epilogue and going by the current release schedule it should come out early next year.

I highly recommend reading the books if anyone is interested in this series. I just rewatched season 1 in anticipation of season 2 and while it was a great adaptation, I found myself explaining a lot of extra details that got skipped to my brother after each episode.