Currently still reading, but will finish tomorrow: "Clear and Simple as the Truth" by Francis-Noël Thomas and Mark Turner.
This is the only book I know that discusses that there are several styles of writing and that exhibits one particular style that the authors call "classic style".
They also discuss differences from other styles ("practical style" as taught by Joseph Williams – my other favorite book about writing, that I like even more).
The book is split into three parts: an essay part that talks about the style, "The Museum" with examples of the style from other publications, and "The Studio" with practical tips and exercises.