In the ending of the Higehiro light novel, the main characters' relationships reach a certain resolution. The story likely wraps up the various emotional arcs and developments that have been building throughout the narrative.
It depends on your taste. If you've been following the 'higehiro' series and enjoyed the previous volumes, then volume 5 is likely to be worth it as it will probably continue the story in an interesting way.
The ending of the HigEHiro light novel is quite unexpected and leaves readers with a sense of bittersweet closure. Without spoiling too much, it ties up most of the loose ends for the main characters.
Well, in the end of the Higehiro light novel, there were some unexpected plot twists and the relationships among the characters evolved in interesting ways. It tied up most loose ends neatly.