Art is good, story it's as enjoyable as in Gokinjo, it's deeper than ParaKiss (especially if you watched the ParaiKss anime only. They cut the events of the final two volumes there, right when and where Ai Yazawa packed the full punch, meaning-wise and emotion-wise), and the dramatic and rock music bits can be considered as an appetizer to Nana - just in a more concise form, but they're still effective -.
Considering its (relative) shortness, it gives you a good cast of characters, each one with a different personality and with some unexpected facets being revealed ; it has a good plot and a nice, moving ending, with a meaningful message, just slightly bittersweet. It has dark and sad moments, and the aforementioned rock music elements the artist developed later in Nana. In this case, though, I find the characters to be more likeable than in Nana (the classmates-turned-detectives kids are especially adorable): because, yes, there are the adults , namely Eve/Mizuki, but the kids are equally important for the development to the story and for leading the story to its solution. The interweaving of their POV is very interesting and enjoyable too.
Moreover, you have temporal plane shifts, love stor(ies), a bit of a detective story, and supernatural twists. A lot of elements, but handled very well in every aspect IMO.
A great work indeed