The closest thing to an English translation of Cuisine de Reference is: Practical Kitchen Work; The Basic Arts of Cooking, by (duh) Maincent-Morel. It's a very expensive book, but a web check for used copies shows they're around for well under $20.
A friend has it, I borrowed it to look it over, and think the book is stuck in the eighties -- but to each his own. On the one hand, the most basic techniques don't change much, even if presentations and styles do; but on the other, we're not talking about a fried pork chop and two veg -- high end food is very trendy. It's a good idea to find a few books which are good on technique AND au courant.
I'm all for reading the classics from Escoffier, Pellaprat, Mme St Ainge, etc., but don't think you'll get much insight into modern cooking or garner many recipes which are usable today. There are just so many things we don't do or serve which were popular before WWII. I learned quite a bit of what I know from Pellaprat in particular, but there are easier and more efficient ways to go about learning.
As an observation: When someone recommends learning to cook from the classic writers, Escoffier in particular, he's usually (but not always) saying more about himself and/or the type of food he likes than about learning to cook at home or professionally in the modern world. After all, why not recommend Careme as enthusiastically? One thing you do learn from the classic chefs is that each was a revolutionary force in his or her own time, and that the essence of each chef's revolution was a celebration ingredients and simplicity. Certainly, there's no better lesson than that. Nor can it be denied that the classic writers are good for modern inspiration. BUT it's a good idea to bear in mind that there's not a lot of demand for cuisses de nymphes à l'aurore any more.
For someone like Nathan, Mastering the Art of French Cooking I and II, by Julia Child, et al is going to be a helluva lot more useful. But sad to say, while it's a lot more practical Child is quite dated as well.
I recently received a Modernist Cuisine At Home, by Myhrvold and Bilet, and it as up to date for both techniques and recipes -- although it's also quite expensive. The professional, 5 volume version is more complete, but is impractically expensive and probably inappropriate for Nathan's skill level. He can dip a toe into it and see if it suits for free by downloading the .pdf version.
BDL