Horimiya is a mixed bag of a series. Up to roughly Vol 8 of the manga I would give this an overall score of 8 or even 9; the characters are interesting and the plot engaging. However, around Vol 9, the author pivots the series from one driven by (main) character development to one that effectively presents a series of standalone vignettes. A few new characters are introduced at this point, which gives some slightly different dynamics for the author to have fun with, but there ceases to be any development of either of the main characters or the world at large.
While I can somewhat understand this change (it is financial advantageous to pad out the series once people are engaged and some readers will enjoy simply spending time in the world they're invested in), it ultimately makes the second half of the manga fun, but hollow and unsatisfying (a 6/10 if you will).
With the final volume being released soon I expect that the author will aim for some closure with the core protagonists of the story, however, it may very well be that you could skip 4 or 5 volumes of the manga and simply not miss out on any major plot points and that represents both a lack of conviction on the part of the author and a missed opportunity to make something even more engrossing.