"Some of the recipes in the book have evolved for us. Many haven't"

This quote by Thomas Keller speaks with the idea of evolution and adjustment. He is suggesting that a few of the recipes in the book have actually altered with time, adapting to the needs and tastes of the people who use them. This could indicate that the dishes have been modified to make them much easier to prepare, or to make them more delicious. It might also imply that the active ingredients have been changed to show the availability of certain components in various regions. On the other hand, Keller is also suggesting that some recipes have actually remained the same, either due to the fact that they are timeless classics or due to the fact that they are so beloved that they have actually not needed to be changed. This quote speaks with the idea that recipes are living files, constantly developing to meet the needs of individuals who utilize them.