Mahou Sekai no Uketsukejou ni Naritai desu is a fun romantic comedy that, despite its third novel ending on a fairly conclusive note, decides to keep going anyway. With the main plotline concluded and their relationship free of misunderstandings I’m not really sure where else it can go.
Koutei-tsuki Nyokan wa Hanayome toshite Nozomarechuu is a four book series that’s three books too long. The first novel solves basically every notable issue with the continuations primarily being a procession of manufactured complications, each less believable than the last. That said, the fourth book is the best ending point you could ask for… it’s just that I don’t feel it’s worth wading through all the weirdness of the third to reach.