This is the 3827th most frequent Japanese word.
よき
"よき" means "good" or "pleasant."
In this sentence, 'よき' is used as an adjective meaning 'good,' emphasizing the positive quality of the hypothetical friendship with the book.
この本は実に素晴らしく、よき友になるでしょう。
This book is truly wonderful and will become a good friend.
Here, 'よき' is utilized to describe 'leaders,' indicating their positive qualities and effectiveness in their role.
よきリーダーは常にチームを導く方法を知っています。
A good leader always knows how to guide the team.
In this sentence, 'よき' modifies 'times,' conveying nostalgia for the favorable attributes of past eras.