First of all, I'd like to say that I really like the feel of this story. You've conveyed the mood very well, and through a combination of the cover and the writing style, I really got the soft, bright mood coming through in your words. Almost like an angelic light cast over it. Also, the premise is great - truly original.
-While the French words lend a really cool and unique feel to this story, I'm not sure that they're right for your audience. I like the footnotes, but the meaning of some of the words - like "mariniere" were lost on me. But that's not too important.
-In chapter one, the paragraph starting with "They went down the elevator...", you have a typo after the cafe footnote. "My" should be replaced with "by".
-Why is all of the dialogue italicized in the first chapter, but nowhere else?
-You have a spare quotation mark at the end of the line "I don't care, Francois..." (chapter 2).
-I'm just a little confused about whether or not the Phenomenes are common knowledge. Does everyone know them and what they entail? And are they human?
-This is a petty little detail but in Livre Premier 2, in the third paragraph, it should be "A woman as young as she..."
-In the same chapter you have a fragment. Maybe you could change it to "The weather, life in Paris, Wilhelmina's father, Francois' parents,brother and sister, all came up while he sipped on a hot cafe au lait."
All in all, though...Wow. You're a phenomenal writer (no pun intended). Seriously, I think this captured just the perfect mood without feeling rushed or tacky or forced. Everything flowed perfectly, and it's really hard to give you criticism beyond a few typos. Please keep the story going, it's fantastic!