(Note that I have not read the LN) Boogiepop Phantom is a very interesting piece of entertainment as there are 3 ways to enjoy it be it by Light Novel, Anime, or Manga (which is what I am reviewing) But this may be a common thing to most other anime with an anime, manga, LN, etc. Each version of Boogiepop is radically different from each other in the sense of tone, style, and pacing.
The story is similar to the 2019 show except it is a bit slower in pace but that helps flesh out things anyway. The story starts in an archaic tone
with Boogiepop coming to the aid of the crying man. The story is more linear than the show which is not a bad thing.
The art is decent. It does not really strike out as anything amazing and it could be rough at times. Good points with the art is the use of shadows making things seem more ominous in tone which is what the Boogiepop anime from 2000 excelled at. The faces were hard to tell apart as well (I could only tell people apart by hair lol)
I could go on about how Boogiepop is a coolass character but what the manga was really about (which is a good point) was the side characters. They all go through a bit of characterization unlike the 2019 anime which was mainly focused on Boogiepop.
Enjoyment and overall:
Overall I would give it a 6 it added a bit of enjoyment towards the shows and seeing the characters go through a bit more characterization (which is probably how the LN went) So if you are a diehard Boogiepop fan I'd say give it a read and check how it differs from other adaptations.