I'm a librarian who loves anime, manga, and reading a wide variety of genres.
The structure of this series:
Clover 1 - Confusing action that doesn't feel like action because of how CLAMP drew it all. This thing is style over clarity, but it's so pretty I can almost forgive it.
Clover 2 - Finally, a few explanations. And tragedy.
Clover 3 - A giant flashback.
Clover 4 - I only just started this, but it looks like it's an even deeper flashback, to the time before Clover 3's flashback.
Throughout everything: song lyrics in a fancy font that's a bit too hard for me to read. So I've stopped trying.
I've heard that this series was supposed to be a couple volumes longer but was ended prematurely, so I'm bracing myself for a frustrating ending.