This is one of my most favorite mangas of all time because of only one thing -- the unique way with which romance is presented. Romance is a well-worn subject in culture and art, and though the ideas in the manga has been thoroughly explored in other media -- saying no to the advances of a guy, sweeping a girl off her feet with a romantic approach, etc.etc. -- I have never read about it in the way it is treated in this manga.
The most artful illustrations in the manga are during dream sequences of Tsubaki. My most favorite dream sequence is the one where Tsubaki and Urabe is dancing -- I thought at that time, "What a great way to think about falling in love!"
Overall, I like this manga for its originality, and the weird yet delightful way with which relationships are presented. I look forward to what will happen to the characters in "Nazo no Kanojo X" in the future.