NEW. FRESH CONCEPT. I LOVED IT. 
 Would like Firebirds to exist? I'm still uncertain. 
 Pros: if a loved one died prematurely, you can go into another dimension and find him/her. You could choose to steal the life of one of your versions to make it your own to live. You could have access to anything. Really. Even if temporarily. 
 Cons: I'm a girl who forgets things way too easily. I would forget who's who in a matter of hours and then it would be a catastrophe of epic proportions. 
 Thank God our Marguerite isn't like me, she doesn't think twice about doing multidimensional travels, she just does. 
 Her character has a strong psychological development, she goes through a hell of a lot in a matter of days and she still plays it cool on the outside (the inside... Well that's another story). 
 I WOULD HAVE FREAKED OUT IMMEDIATELY LOL. 
 Same for Paul and Theo. Two amazing characters, completely different in their behavior, but with the same amount of love for (view spoiler)[ Marguerite (hide spoiler)] and their studies. 
 I loved how Claudia focused a lot on family, or lack of it even. She described the feelings Marguerite was going through perfectly. Actually, this entire book is perfectly written. 
 Gosh I'd have tons of other things to say, but they'd be a bunch of spoilers.... So let's end this here, shall we? 
 Anyway, definitely recommended if you want to read something similar to time travel but that actually has no time travel in it! :)