If you are truly looking for the best, Larousse Gastronomique tops my list. I don't think a more exhaustive cookbook has ever been written.
The Larousse Gastronomique is amazing.
Larousse Gastronomique: The World's Greatest Culinary Encyclopedia, Completely Revised and Updated https://www.amazon.com/dp/0307464911/ref=cm_sw_r_cp_api_glc_fabc_LkM1FbZP4SQAY
Gastronomique is an incredible resource for all pretty much anything edible.
Harold McGee's On Food and Cooking is also a great resource but is more like a text book than a cook book.
The Ideas in Food books are pretty good too.
I guess I've been leaning more towards "educational" type reading lately (opposed to recipe tomes). Ratio is also very good. Does reddit like Ruhlman?
As a Chef, I recommend Larousse http://www.amazon.com/Larousse-Gastronomique-Greatest-Encyclopedia-Completely/dp/0307464911